Force measurement assembly

ABSTRACT

A force measurement assembly is disclosed herein. The force measurement assembly includes a top component, the top component having a top surface for receiving at least one portion of the body of the subject; a single force transducer supporting the top component, the single force transducer configured to sense one or more measured quantities and output one or more signals that are representative of forces and/or moments being applied to the top surface of the top component by the subject; and a base component disposed underneath the single force transducer, the base component configured to be disposed on a support surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of U.S. Nonprovisionalpatent application Ser. No. 17/367,599, entitled “Force MeasurementSystem”, filed on Jul. 5, 2021; which is a continuation-in-part of U.S.Nonprovisional patent application Ser. No. 17/013,812, entitled “ForceMeasurement System”, filed on Sep. 7, 2020, now U.S. Pat. No.11,054,325; which is a continuation-in-part of U.S. Nonprovisionalpatent application Ser. No. 16/735,411, entitled “Force MeasurementSystem”, filed on Jan. 6, 2020, now U.S. Pat. No. 10,765,936; whichclaims priority to U.S. Provisional Patent Application No. 62/957,178,entitled “Body Sway Measurement System”, filed on Jan. 4, 2020, and is acontinuation-in-part of U.S. Nonprovisional patent application Ser. No.16/186,512, entitled “Force Measurement System and a Method ofCalibrating the Same”, filed on Nov. 10, 2018, now U.S. Pat. No.10,527,508; which is a continuation-in-part of U.S. Nonprovisionalpatent application Ser. No. 15/721,951, entitled “Load TransducerSystem”, filed on Oct. 1, 2017, now U.S. Pat. No. 10,126,186; which is acontinuation-in-part of U.S. Nonprovisional patent application Ser. No.15/224,419, entitled “Load Transducer and Force Measurement AssemblyUsing the Same”, filed on Jul. 29, 2016, now U.S. Pat. No. 9,778,119;which is a continuation-in-part of U.S. Nonprovisional patentapplication Ser. No. 14/714,797, entitled “Load Transducer and ForceMeasurement Assembly Using the Same”, filed on May 18, 2015, now U.S.Pat. No. 9,404,823; which is a continuation-in-part of U.S.Nonprovisional patent application Ser. No. 14/158,809, entitled “LowProfile Load Transducer”, filed on Jan. 18, 2014, now U.S. Pat. No.9,032,817; and further claims the benefit of U.S. Provisional PatentApplication No. 61/887,357, entitled “Low Profile Load Transducer”,filed on Oct. 5, 2013, the disclosure of each of which is herebyincorporated by reference as if set forth in their entirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK

Not Applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to a force measurement system. Moreparticularly, the invention relates to a force measurement system havinga plurality of force measurement assemblies where at least some of theplurality of force measurement assemblies that are disposed underneath asubject varies over time.

2. Background and Related Art

The use of strain gages in load transducers to measure forces andmoments is a known art. A transducer can incorporate one or more loadchannels. Each load channel measures one of the load components, and iscomprised of one or more strain gages mounted to one or more elasticelements that deform under the applied load. An appropriate circuitryrelates the resistance change in each set of gages to the applied forceor moment. Strain gages have many industrial, medical, and electricalapplications due to their small size, low production cost, flexibilityin installation and use, and high precision.

A typical low profile, small, multi-component load transducer onlyfunctions correctly when the axial (i.e. vertical) force acts relativelycentral to the transducer. Specifications of such transducers indicate amaximum allowable offset for the force being approximately half thediameter of the transducer. Technical specifications of transducers aregiven as the allowable force and moment ratings, where the moment ratingis obtained by multiplying the maximum allowable force with the maximumallowable offset of the force.

Transducers can be used to measure forces and moments in linkages suchas those found in a robotic arm, where the links are connected byjoints, and the magnitude and offset of the forces transmitted by thesejoints are used to control the linkage. In such applications, it isdesirable to have a transducer which has significantly higher momentcapacity than those available in the market. Accordingly, there is aneed for an improved multi-component, low profile load transducer withhigh moment capacity.

When conventional load transducers are utilized in conjunction withforce plates, unique load transducers must be designed and fabricatedfor force plates having a particular footprint size. Consequently, inorder to fit force plates with varying footprint sizes, many differentcustom load transducers are required. These custom load transducerssignificantly increase the material costs associated with thefabrication of a force plate. Also, conventional load transducers oftenspan the full length or width of the force plate component to which theyare mounted, thereby resulting in elongate load transducers that utilizean excessive amount of stock material.

Therefore, what is needed is a load transducer that is capable of beinginterchangeably used with a myriad of different force plate sizes sothat load transducers that are specifically tailored for a particularforce plate size are unnecessary. Moreover, there is a need for auniversal load transducer that is compact and uses less stock materialthan conventional load transducers, thereby resulting in lower materialcosts. Furthermore, there is a need for a force measurement assemblythat utilizes the compact and universal load transducer thereon so as toresult in a more lightweight and portable force measurement assembly.

Also, certain strain gages or strain gage pairs of a typicalmulti-component load transducer are configured to be sensitive to aparticular component of the applied load (i.e., to a particular one ofthe force or moment components being measured). However, because thebody portion of a typical load transducer has unavoidable machiningimperfections, and the strain gages are not perfectly positioned on thebody of the load transducer, there is some crosstalk between thechannels of the load transducer. For example, a channel that is intendedto be sensitive only to the x-component of the force may also emit anon-zero output signal when only a vertical force is applied to the loadtransducer (i.e., when the z-component of the force is applied). Thus,in such a typical load transducer, there is undesirable crosstalkbetween the channels.

Moreover, the output of a typical multi-component load transducer isalso undesirably affected by the ambient temperature of the environmentin which the load transducer is disposed. For example, the accuracy of aload output signal of a load transducer that is disposed in a spacehaving a high ambient temperature (e.g., a space with a temperature of140 degrees or more) will be adversely affected by the high ambienttemperature. That is, high ambient temperature will introduceinaccuracies in the load output signal.

Furthermore, the position of the applied load may also adversely affectthe accuracy of the output signal of a typical multi-component loadtransducer. For example, when the load is applied at a location that isnear the periphery of the measurement surface of the load measurementdevice in which the load transducer is installed, the load output of theload transducer is often less accurate than when the load is appliedproximate to the center of the measurement surface of the loadmeasurement device. As such, the measurement accuracy of a typical loadmeasurement device undesirably varies depending upon the position of theload applied thereto.

Therefore, what is also needed is a load transducer system that iscapable of correcting the output signal of a load transducer so as toreduce or eliminate the effects of crosstalk among the channels of theload transducer. In addition, there is a need for a load transducersystem that is capable of correcting the output signal of a loadtransducer so as to reduce or eliminate the effects of changes intemperature on the output of the load transducer. Further, there is aneed for a load transducer system that is capable of accuratelydetermining the applied load regardless of the location of the appliedload being measured by the load transducer.

Further, force plates historically have been calibrated by applyingknown loads at known locations and using the collected data to form acalibration matrix. This unique calibration matrix, stored on the forceplate, converts the raw signal input into a calibrated force output.This methodology provides a global calibration for the force plate.However, the global calibration of the force plate can result inunacceptable errors for certain regions of the force plate (e.g., nearthe edges of the force plate), and can also result in unacceptableerrors for force plates having non-standard shapes (e.g., force plateswith top plate components having shapes other than a rectangular shape).

Therefore, what is additionally needed is a force measurement systemthat allows for more versatile transducer designs and minimizesmeasurement errors. Moreover, a force measurement system is needed thatis capable of correcting for load measurement errors resulting fromloads applied near the periphery of the force measurement assembly.Furthermore, a need exists for a load calibration process for a forcemeasurement system that results in more accurate load measurements bycorrecting the computed load based upon the applied position of theload. In addition, a force measurement system is needed that is capableof assessing the fall risk of a subject based upon a combination ofbalance parameters. Also, a force measurement system is needed thatemploys a compact arrangement of force plates that is capable ofaccurately assessing the gait of a subject when the subject walks orruns on the force measurement system.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

Accordingly, the present invention is directed to a force measurementassembly that substantially obviates one or more problems resulting fromthe limitations and deficiencies of the related art.

In accordance with one or more embodiments of the present invention,there is provided a force measurement assembly configured to receive asubject, which includes a top component, the top component having a topsurface for receiving at least one portion of the body of the subject; asingle force transducer supporting the top component, the single forcetransducer configured to sense one or more measured quantities andoutput one or more signals that are representative of forces and/ormoments being applied to the top surface of the top component by thesubject; and a base component disposed underneath the single forcetransducer, the base component configured to be disposed on a supportsurface.

In a further embodiment of the present invention, the single forcetransducer is disposed proximate to a center of the top component.

In yet a further embodiment, the single force transducer supports theentire weight of the top component.

In still a further embodiment, the single force transducer is in a formof a pylon-type force transducer.

In yet a further embodiment, the single force transducer comprises aforce transducer beam.

In still a further embodiment, the single force transducer is configuredto measure at least one force component and at least one momentcomponent.

In yet a further embodiment, the single force transducer is configuredto measure a plurality of force components and a plurality of momentcomponents.

In still a further embodiment, the top component is in a form of a topplate with the top surface for receiving the at least one portion of thebody of the subject.

In yet a further embodiment, the base component is in a form of a bottomplate configured to be disposed on the support surface.

In still a further embodiment, the force measurement assembly furthercomprises a data processing device operatively coupled to the forcemeasurement assembly, the data processing device configured to receivethe one or more signals that are representative of the forces and/ormoments being applied to the top surface of the top component by thesubject, and to convert the one or more signals into output forcesand/or moments.

It is to be understood that the foregoing summary and the followingdetailed description of the present invention are merely exemplary andexplanatory in nature. As such, the foregoing summary and the followingdetailed description of the invention should not be construed to limitthe scope of the appended claims in any sense.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a perspective view of a low profile load transducer, accordingto a first embodiment of the invention;

FIG. 2 is a first side view of the low profile load transducer of FIG. 1, according to the first embodiment of the invention;

FIG. 3 is a second side view of the low profile load transducer of FIG.1 , according to the first embodiment of the invention;

FIG. 4 is a top view of the low profile load transducer of FIG. 1 ,according to the first embodiment of the invention;

FIG. 5 is a block diagram illustrating data manipulation operationscarried out by the load transducer data processing system, according toan embodiment of the invention;

FIG. 6 is a perspective view of a low profile load transducer, accordingto a second embodiment of the invention;

FIG. 7 is a first side view of the low profile load transducer of FIG. 6, according to the second embodiment of the invention;

FIG. 8 is a second side view of the low profile load transducer of FIG.6 , according to the second embodiment of the invention;

FIG. 9 is a top view of the low profile load transducer of FIG. 6 ,according to the second embodiment of the invention;

FIG. 10 is a perspective view of a low profile load transducer,according to a third embodiment of the invention;

FIG. 11 is a first side view of the low profile load transducer of FIG.10 , according to the third embodiment of the invention;

FIG. 12 is a second side view of the low profile load transducer of FIG.10 , according to the third embodiment of the invention;

FIG. 13 is a top view of the low profile load transducer of FIG. 10 ,according to the third embodiment of the invention;

FIG. 14 is a bottom view of the low profile load transducer of FIG. 10 ,according to the third embodiment of the invention;

FIG. 15 is a perspective view of a low profile load transducer,according to a fourth embodiment of the invention;

FIG. 16 is a first side view of the low profile load transducer of FIG.15 , according to the fourth embodiment of the invention;

FIG. 17 is a second side view of the low profile load transducer of FIG.15 , according to the fourth embodiment of the invention;

FIG. 18 is a top view of the low profile load transducer of FIG. 15 ,according to the fourth embodiment of the invention;

FIG. 19 is a perspective view of a low profile load transducer,according to a fifth embodiment of the invention;

FIG. 20 is a perspective view of a low profile load transducer,according to a sixth embodiment of the invention;

FIG. 21 is a perspective view of a low profile load transducer,according to a seventh embodiment of the invention;

FIG. 22 is a perspective view of a low profile load transducer,according to an eighth embodiment of the invention;

FIG. 23 is a perspective view of a low profile load transducer,according to a ninth embodiment of the invention;

FIG. 24 is a perspective view of a low profile load transducer,according to a tenth embodiment of the invention;

FIG. 25 is a perspective view of an exemplary mounting arrangement forthe low profile load transducer illustrated in FIGS. 15-18 ;

FIG. 26 is a top perspective view of a load transducer, according to aneleventh embodiment of the invention;

FIG. 27 is a first side view of the load transducer of FIG. 26 ,according to the eleventh embodiment of the invention;

FIG. 28 is a second side view of the load transducer of FIG. 26 ,according to the eleventh embodiment of the invention;

FIG. 29 is a bottom perspective view of the load transducer of FIG. 26 ,according to the eleventh embodiment of the invention;

FIG. 30 is a top perspective view of a load transducer, according to atwelfth embodiment of the invention;

FIG. 31 is a first side view of the load transducer of FIG. 30 ,according to the twelfth embodiment of the invention;

FIG. 32 is a second side view of the load transducer of FIG. 30 ,according to the twelfth embodiment of the invention;

FIG. 33 is a bottom perspective view of the load transducer of FIG. 30 ,according to the twelfth embodiment of the invention;

FIG. 34 is a perspective view of a force measurement system thatutilizes the load transducer of FIG. 30 , according to an embodiment ofthe invention;

FIG. 35 is a bottom, assembled perspective view of the force measurementassembly of the force measurement system of FIG. 34 ;

FIG. 36 is a bottom, partially exploded perspective view of the forcemeasurement assembly of the force measurement system of FIG. 34 ;

FIG. 37 is a block diagram of constituent components of the forcemeasurement systems of FIGS. 34 and 42 ;

FIG. 38 is a block diagram illustrating data manipulation operationscarried out by the force measurement systems of FIGS. 34 and 42 ;

FIG. 39 is a top perspective view of a load transducer, according to athirteenth embodiment of the invention;

FIG. 40 is a side view of the load transducer of FIG. 39 , according tothe thirteenth embodiment of the invention;

FIG. 41 is a top plan view of the load transducer of FIG. 39 , accordingto the thirteenth embodiment of the invention;

FIG. 42 is a bottom, assembled perspective view of a force measurementsystem that utilizes the load transducer of FIG. 39 , according to anembodiment of the invention;

FIG. 43 is a bottom, partially exploded perspective view of the forcemeasurement assembly of the force measurement system of FIG. 42 ;

FIG. 44 is a top perspective view of a load transducer, according to afourteenth embodiment of the invention;

FIG. 45 is a side view of the load transducer of FIG. 44 , according tothe fourteenth embodiment of the invention;

FIG. 46 is a top plan view of the load transducer of FIG. 44 , accordingto the fourteenth embodiment of the invention;

FIG. 47 is a top perspective view of a load transducer, according to afifteenth embodiment of the invention, wherein the load transducer ofFIG. 47 is configured for a left side mounting arrangement on the forcemeasurement assembly;

FIG. 48 is a top perspective view of a load transducer that is generallysimilar to the load transducer of FIG. 47 , except that the loadtransducer of FIG. 48 is configured for a right side mountingarrangement on the force measurement assembly rather than a left sidemounting arrangement;

FIG. 49 is a bottom, assembled perspective view of a force measurementassembly that utilizes the load transducers of FIGS. 47 and 48 ,according to another embodiment of the invention;

FIG. 50 is a bottom, partially exploded perspective view of the forcemeasurement assembly of FIG. 49 ;

FIG. 51 is a top perspective view of a load transducer, according to asixteenth embodiment of the invention;

FIG. 52 is a first side view of the load transducer of FIG. 51 ,according to the sixteenth embodiment of the invention;

FIG. 53 is a second side view of the load transducer of FIG. 51 ,according to the sixteenth embodiment of the invention;

FIG. 54 is a top plan view of the load transducer of FIG. 51 , accordingto the sixteenth embodiment of the invention;

FIG. 55 is a perspective view of a load transducer, according to aseventeenth embodiment of the invention;

FIG. 56 is a front elevational view of the load transducer of FIG. 55 ;

FIG. 57 is a rear elevational view of the load transducer of FIG. 55 ;

FIG. 58 is a side view of the load transducer of FIG. 55 ;

FIG. 59 is a top view of the load transducer of FIG. 55 ;

FIG. 60 is a transverse cross-sectional view of the load transducer ofFIG. 55 , wherein the transverse section is cut through the cuttingplane line A-A in FIG. 56 ;

FIG. 61 is a perspective view of a load transducer, according to aneighteenth embodiment of the invention;

FIG. 62 is a front elevational view of the load transducer of FIG. 61 ;

FIG. 63 is a rear elevational view of the load transducer of FIG. 61 ;

FIG. 64 is a side view of the load transducer of FIG. 61 ;

FIG. 65 is a top view of the load transducer of FIG. 61 ;

FIG. 66 is a transverse cross-sectional view of the load transducer ofFIG. 61 , wherein the transverse section is cut through the cuttingplane line B-B in FIG. 62 ;

FIG. 67 is a block diagram illustrating data manipulation operationscarried out by the load transducer data processing system, according toan embodiment of the invention;

FIG. 68 is a block diagram of constituent components of the loadtransducer system, which utilizes the load transducer of FIG. 55 or FIG.61 , according to an embodiment of the invention;

FIG. 69 is a signal flow diagram for the load transducer systemdescribed herein, which utilizes the load transducer of FIG. 55 or FIG.61 , according to an embodiment of the invention;

FIG. 70 is a perspective view of a top plate component of a forcemeasurement assembly, according to an embodiment of the invention,wherein load calibration points disposed in grid arrangements areillustrated on the top and side surfaces of the top plate component;

FIG. 71 is a perspective view of a top plate component of a forcemeasurement assembly, according to an embodiment of the invention,wherein the load calibration points for a particular one of the loadregions are illustrated in emphasized form on the top and side surfacesof the top plate component;

FIG. 72 is a flowchart illustrating a calibration procedure for a forcemeasurement assembly carried out by the force measurement systemillustrated in FIGS. 42, 70, and 71 , according to an embodiment of theinvention;

FIG. 73 is a flowchart illustrating a first load correction procedurefor a force measurement assembly carried out by the force measurementsystem illustrated in FIGS. 42, 70 , and 71, according to an embodimentof the invention;

FIG. 74 is a flowchart illustrating a second load correction procedurefor a force measurement assembly carried out by the force measurementsystem illustrated in FIGS. 42, 70 , and 71, according to an embodimentof the invention;

FIG. 75 is a diagrammatic perspective view of a first exemplary forcemeasurement system for measuring the center of pressure and body sway ofa subject, according to a further embodiment of the invention;

FIG. 76 is a diagrammatic perspective view of a second exemplary forcemeasurement system for measuring the center of pressure and body sway ofa subject, according to yet a further embodiment of the invention;

FIG. 77 is a bottom, assembled perspective view of a first type of forcemeasurement assembly used in the force measurement systems of FIGS. 75and 76 ;

FIG. 78 is a bottom, exploded perspective view of the force measurementassembly of FIG. 77 ;

FIG. 79 is a bottom, assembled perspective view of a second type offorce measurement assembly used in the force measurement systems ofFIGS. 75 and 76 ;

FIG. 80 is a bottom, exploded perspective view of the force measurementassembly of FIG. 79 ;

FIG. 81 is a bottom, assembled perspective view of a force measurementassembly, according to still a further embodiment of the invention;

FIG. 82 is a top plan view of the force measurement assembly of FIG. 81;

FIG. 83 is a transverse cross-sectional view of the force measurementassembly of FIG. 81 , wherein the transverse section is cut through thecutting plane line C-C in FIG. 82 ;

FIG. 84 is a bottom, assembled perspective view of a force measurementassembly, according to yet a further embodiment of the invention;

FIG. 85 is a top plan view of the force measurement assembly of FIG. 84;

FIG. 86 is a transverse cross-sectional view of the force measurementassembly of FIG. 84 , wherein the transverse section is cut through thecutting plane line D-D in FIG. 84 ;

FIG. 87 is a bottom, assembled perspective view of a force measurementassembly, according to still a further embodiment of the invention;

FIG. 88 is a top plan view of the force measurement assembly of FIG. 87;

FIG. 89 is a transverse cross-sectional view of the force measurementassembly of FIG. 87 , wherein the transverse section is cut through thecutting plane line E-E in FIG. 87 ;

FIG. 90 is a top perspective view of an independently displaceable forcemeasurement assembly of a force measurement system, according to yet afurther embodiment of the invention;

FIG. 91 is a side elevational view of the force measurement assembly ofFIG. 90 ;

FIG. 92 is a bottom plan view of the force measurement assembly of FIG.90 ;

FIG. 93 is a top plan view of a force measurement system comprising aplurality of independently displaceable force measurement assemblies,wherein the plurality of independently displaceable force measurementassemblies are arranged in a first linear arrangement;

FIG. 94 is another top plan view of the force measurement system of FIG.93 , wherein one of the force measurement assemblies is shown beingdisplaced to a first position along a side of the other forcemeasurement assemblies in the system;

FIG. 95 is yet another top plan view of the force measurement system ofFIG. 93 , wherein the displaced one of the force measurement assembliesis shown being displaced to a further second position along the side ofthe other force measurement assemblies in the system;

FIG. 96 is still another top plan view of the force measurement systemof FIG. 93 , wherein the displaced one of the force measurementassemblies is shown being displaced to a third position in front of theother force measurement assemblies in the system;

FIG. 97 is a perspective view of a force measurement system comprising aplurality of independently displaceable force measurement assembliesarranged in a matrix configuration;

FIG. 98 is an assembled perspective view of a force measurementassembly, according to still a further embodiment of the invention;

FIG. 99 is another assembled perspective view of the force measurementassembly of FIG. 98 ;

FIG. 100 is a side elevational view of the force measurement assembly ofFIG. 98 ;

FIG. 101 is an exploded perspective view of the force measurementassembly of FIG. 98 ;

FIG. 102 is a top plan view illustrating two (2) of the forcemeasurement assemblies of FIG. 98 arranged in a first configuration;

FIG. 103 is a top plan view illustrating two (2) of the forcemeasurement assemblies of FIG. 98 arranged in a second configuration;

FIG. 104 is a top plan view illustrating four (4) of the forcemeasurement assemblies of FIG. 98 arranged in a third configuration; and

FIG. 105 is a top plan view illustrating six (6) of the forcemeasurement assemblies of FIG. 98 arranged in a fourth configuration.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the load transducers and theforce measurement systems as disclosed herein, including, for example,specific dimensions, orientations, locations, and shapes of the variouscomponents, will be determined in part by the particular intendedapplication and use environment. Certain features of the illustratedembodiments have been enlarged or distorted relative to others tofacilitate visualization and clear understanding. In particular, thinfeatures may be thickened, for example, for clarity or illustration. Allreferences to direction and position, unless otherwise indicated, referto the orientation of the load transducers illustrated in the drawings.In general, up or upward generally refers to an upward direction withinthe plane of the paper in FIG. 1 and down or downward generally refersto a downward direction within the plane of the paper in FIG. 1 .

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

It will be apparent to those skilled in the art, that is, to those whohave knowledge or experience in this area of technology, that many usesand design variations are possible for the improved load transducers andforce measurement systems disclosed herein. The following detaileddiscussion of various alternative and preferred embodiments willillustrate the general principles of the invention. Other embodimentssuitable for other applications will be apparent to those skilled in theart given the benefit of this disclosure.

Referring now to the drawings, FIGS. 1-4 illustrate a load transducer 10according to a first exemplary embodiment of the present invention. Thisload transducer 10 is designed to have a low profile, small size,trivial weight, high sensitivity, and easy manufacturability. The loadtransducer 10 generally includes a one-piece compact transducer frame 12having a central body portion 14 and a plurality of beams 16, 18, 20,22, 24, 26, 28, 30 extending outwardly from the central body portion 14.As best illustrated in the perspective view of FIG. 1 , each of thebeams 16, 18, 20, 22, 24, 26, 28, 30 comprises a respective load cell ortransducer element for measuring forces and/or moments. For example, theload cells of beams 16, 18, 24, 26 are configured to respectivelymeasure the forces F1, F2, F3, F4 with force vector components F1 _(x),F1 _(y), F1 _(z), F2 _(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z),F4 _(x), F4 _(y), F4 _(z). In addition to forces, the output of the loadcells can also be used to determine moments and the point of applicationof a force (i.e., its center of pressure). Referring again to FIG. 1 ,it can be seen that the illustrated load transducer 10 comprises eightsingle or multi-axis load cells that are mounted to a common structureor body portion 14.

The illustrated transducer frame 12 is shown in FIGS. 1-4 . Theillustrated transducer frame 12 includes the central body portion 14 anda plurality of beams 16, 18, 20, 22, 24, 26, 28, 30 extending outwardlytherefrom. In the illustrated embodiment, the transducer frame 12 ismilled as one solid and continuous piece of a single material. That is,the transducer frame 12 is of unitary or one-piece construction with thebody portion 14 and the beams 16, 18, 20, 22, 24, 26, 28, 30 integrallyformed together. The transducer frame 12 is preferably machined in onepiece from aluminum, titanium, steel, or any other suitable materialthat meets strength and weight requirements. Alternatively, the beams16, 18, 20, 22, 24, 26, 28, 30 can be formed separately and attached tothe body portion 14 in any suitable manner.

With reference to FIG. 1 , it can be seen that the illustrated centralbody portion 14 is generally in the form of rectangular prism (i.e., asquare prism) with substantially planar top, bottom, and side surfaces.In FIG. 1 , it can be seen that the body portion 14 comprises a firstpair of opposed sides 14 a, 14 c and a second pair of opposed sides 14b, 14 d. The side 14 a is disposed generally parallel to the side 14 c,while the side 14 b is disposed generally parallel to the side 14 d.Each of the sides 14 a, 14 b, 14 c, 14 d is disposed generallyperpendicular to the planar top and bottom surfaces. Also, each of thefirst pair of opposed sides 14 a, 14 c is disposed generallyperpendicular to each of the second pair of opposed sides 14 b, 14 d.While not explicitly shown in FIGS. 1-4 , the central body portion 14may comprise one or more apertures disposed therethrough foraccommodating fasteners (e.g., screws) that attach electronics orcircuitry to the body portion 14. In addition to fasteners, it is notedthat any other suitable means for attachment of the electronics orcircuitry can alternatively be utilized (e.g., suitable adhesives,etc.). While the illustrated body portion 14 is generally in the form ofa square prism, it is to be understood that the body portion 14 canalternatively have other suitable shapes.

As shown in FIGS. 1-4 , the illustrated beams 16, 18, 20, 22, 24, 26,28, 30 are each attached to one of the sides 14 a, 14 b, 14 c, 14 d ofthe body portion 14, and extend generally horizontally outwardtherefrom. In particular, beams 16, 18 extend generally horizontallyoutward from side 14 a of the body portion 14, beams 20, 22 extendgenerally horizontally outward from side 14 b of the body portion 14,beams 24, 26 extend generally horizontally outward from side 14 c of thebody portion 14, and beams 28, 30 extend generally horizontally outwardfrom side 14 d of the body portion 14. In addition, each of theillustrated beams 16, 18, 20, 22, 24, 26, 28, 30 extend substantiallyparallel to the top and bottom surfaces of the body portion 14. Each ofthe illustrated beams 16, 18, 20, 22, 24, 26, 28, 30 has a cantileveredend relative to the body portion 14 that allows for deflection of theends of the beams 16, 18, 20, 22, 24, 26, 28, 30 in the verticaldirection.

With particular reference to FIGS. 1 and 4 , it can be seen that thebeams 16, 18 extending from side 14 a are substantially parallel to oneanother, and laterally spaced apart from one another by a gap. Opposedbeams 24, 26, which extend from side 14 c, also are substantiallyparallel to one another, and laterally spaced apart from one another bya gap. Beam 16 extends in a longitudinal direction that is generallyco-linear with, but opposite to the extending direction of beam 26(i.e., both beams 16 and 26 are aligned along central longitudinal axisLA1). Similarly, beam 18 extends in a longitudinal direction that isgenerally co-linear with, but opposite to the extending direction ofbeam 24 (i.e., both beams 18 and 24 are aligned along centrallongitudinal axis LA2). The beams 20, 22 extending from side 14 b aresubstantially parallel to one another, and laterally spaced apart fromone another by a gap. Opposed beams 28, 30, which extend from side 14 d,also are substantially parallel to one another, and laterally spacedapart from one another by a gap. Beam 20 extends in a longitudinaldirection that is generally co-linear with, but opposite to theextending direction of beam 30 (i.e., both beams 20 and 30 are alignedalong central longitudinal axis LA3). Similarly, beam 22 extends in alongitudinal direction that is generally co-linear with, but opposite tothe extending direction of beam 28 (i.e., both beams 22 and 28 arealigned along central longitudinal axis LA4). The illustrated beams 16,18, 20, 22, 24, 26, 28, 30 are provided with generally verticallyextending apertures 32 near their ends for accommodating fasteners thatare used to secure the load transducer 10 to additional structures.Although, it is noted that any other suitable means for attachment ofthe load transducer 10 can alternatively be utilized (e.g., a suitableadhesive for attaching metallic components to one another).

The main body portions of illustrated beams 16, 18, 20, 22, 24, 26, 28,30 have a rectangular-shaped cross section to form generally planar,opposed top and bottom surfaces, and generally planar, opposed sidesurfaces for attachment of load cell components as describedhereinafter. The illustrated beams 16, 18, 20, 22, 24, 26, 28, 30 havegenerally cylindrical end portions, which include the fastener apertures32. As best shown in FIG. 1 , the illustrated top planar surfaces of thebeam main body portions of beams 16, 18, 24, 26 are recessed below thetop surfaces of the beam cylindrical end portions to protect the loadcell components from engagement with the structure to which the loadtransducer 10 is attached, while the illustrated bottom planar surfacesof the beam main body portions of beams 20, 22, 28, 30 are recessedabove the bottom surfaces of the beam cylindrical end portions toprotect the load cell components from engagement with the structure towhich the load transducer 10 is attached. In other words, as shown inFIG. 1 , the cylindrical end portions of beams 16, 18, 24, 26 areprovided with a top standoff portion (i.e., a cylindrical portionprotruding from the top of each beam having the aperture 32), while thecylindrical end portions of beams 20, 22, 28, 30 are provided with abottom standoff portion (i.e., a cylindrical portion protruding from thebottom of each beam having the aperture 32). While not explicitly shownin the figures, beams 16, 18, 20, 22, 24, 26, 28, 30 may also includeapertures disposed therethrough for increasing the deflectability of thebeams 16, 18, 20, 22, 24, 26, 28, 30 as desired (e.g., the aperturescould be disposed below, or adjacent to each of the strain gages 34, 36,38). In order to accommodate these apertures, the length of each beam16, 18, 20, 22, 24, 26, 28, 30 could be extended so that multiple straingages 34, 36 on a common beam could be spaced apart from one anotheralong a length of the beam (i.e., each strain gage 34, 36 would occupy adedicated, respective segment of the beam). It is noted that theseapertures can be of any suitable size and shape as needed and also canbe eliminated if desired. It is further noted that the beams 16, 18, 20,22, 24, 26, 28, 30 can alternatively have other cross-sectional shapesdepending on whether it is desired to have planar surfaces at the topand/or bottom or left and/or right sides for the load cell componentsbut the illustrated rectangular shape is particularly desirable becausethe same frame can be used for multiple configurations of the transducerload cells.

The illustrated one-piece frame 12 has a low profile or is compact. Theterms “low profile” and “compact” are used in this specification and theclaims to mean that the height is substantially smaller than thefootprint dimensions so that the load transducer 10 can be utilized in amechanical joint without significant changes to the mechanical joint.The illustrated one piece frame 12 has a height H that is about 20% itsfootprint width W₁ or W₂ (see FIGS. 2, 3, 7 , and 8). As a result, theload transducer 10 has a low profile or is compact and has a height Hthat is about 20% its footprint width W₁ or W₂. The term “load cell” isused in the specification and claims to mean a load sensing element ofthe load transducer that is capable of sensing one or more loadcomponents of the applied load.

As best shown in FIG. 1 , the illustrated load cells are located onbeams 16, 18, 20, 24, 26, and 30. In the illustrated embodiment, beams22, 28 do not contain any load cells, but, in other embodiments, maycontain load cells with strain gages 38 similar to beams 20, 30. Beams16, 26 also may contain strain gages 36, similar to beams 18, 24, inother embodiments. In a preferred embodiment, each load cell comprisesone or more strain gages 34, 36, 38. Specifically, in the illustratedembodiment, beams 16, 18, 24, 26 each comprise a strain gage 34 disposedon the top surface thereof that is sensitive to the vertical forcecomponent (i.e., a F_(Z) strain gage). Opposed beams 18, 24 also eachcomprise a strain gage 36 disposed on a side surface thereof that issensitive to a first shear force component (i.e., a F_(X) strain gage).Opposed beams 20, 30 each comprise a strain gage 38 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(Y) strain gage). All eight (8) of the strain gages 34, 36,38 are measuring a difference in the bending moments in the beams. Ifthe applied shears to each of the two parallel beams 18, 24 or 20, 30are equal (which is most likely the case), this is an optimal number ofstrain gages for a six-component load transducer (i.e., for a loadtransducer that is capable of measuring the three (3) force componentsF_(X), F_(Y), F_(Z) and the three (3) moment components M_(X), M_(Y),M_(Z)). Shear web gages can also be used in lieu of one or more of theillustrated strain gages 34, 36, 38. Also, in other preferredembodiments alternate load and/or moment sensors may be utilized asrequired or desired as long as they do not interfere with the advantagesof the design as a whole. For example, piezoelectric gages orHall-effect sensors are possible alternatives to the strain gages 34,36, 38.

As best shown in FIG. 1 , the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 34, 36, 38 aremounted to either top or side surfaces of the beams 16, 18, 20, 24, 26,30 between their attachment locations to the body portion 14 and thecylindrical end portions thereof. Alternatively, the strain gages 34 canbe mounted to the bottom surfaces of the beams 16, 18, 24, 26 betweentheir attachment locations to the body portion 14 and the cylindricalend portions thereof, while the strain gages 36, 38 can be mounted tothe opposite side surfaces of the beams 18, 20, 24, 30 between theirattachment locations to the body portion 14 and the cylindrical endportions thereof. That is, the strain gages 34, 36, 38 are mounted tosurfaces generally normal to the direction of applied vertical and/orshear forces (i.e., F_(X), F_(Y), F_(Z)). It is also noted thatalternatively, the strain gages 34 can be mounted at both the topsurface and the bottom surface of the beams 16, 18, 24, 26, and/or thestrain gages 36, 38 can be mounted at both opposed side surfaces of thebeams 18, 20, 24, 30. These strain gages 34, 36, 38 measure force eitherby bending moment or difference of bending moments at two crosssections. As force is applied to the ends of the beams (e.g., forces F1,F2, F3, F4 with force vector components F1 _(x), F1 _(y), F1 _(z), F2_(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4 _(x), F4 _(y), F4_(z) applied to the ends of respective beams 16, 18, 24, 26), the beams16, 18, 20, 24, 26, 30 with strain gages attached thereto bend. Thisbending either stretches or compresses the strain gages 34, 36, 38, inturn changing the resistances of the electrical currents passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force (e.g., forces F1,F2, F3, F4 with force vector components F1 _(x), F1 _(y), F1 _(z), F2_(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4 _(x), F4 _(y), F4_(z) applied to the ends of respective beams 16, 18, 24, 26).

Alternatively, the load cells can be configured as shear-web load cells.In this configuration, the strain gages are mounted to either one of thelateral side surfaces of the beams between their attachment locations tothe body portion 14 and the cylindrical end portions thereof. It isnoted that alternatively, the strain gages can be mounted at both of thelateral side surfaces of the beams. Mounted in these positions, thestrain gages directly measure shear as force is applied to the end ofthe beam.

As best shown in FIG. 1 , the load transducer 10 measures applied forces(e.g., forces F1, F2, F3, F4 with force vector components F1 _(x), F1_(y), F1 _(z), F2 _(x), F2 _(y), F2 _(z), F3 _(x), F3 _(y), F3 _(z), F4_(x), F4 _(y), F4 _(z) applied to the ends of respective beams 16, 18,24, 26) at each of the load cells. The sum of the forces is the forcebeing applied to any assembly attached to the top of the load transducer10. The load cells of the beams 16, 26 measure the force being appliedto one lateral side of the load transducer 10; whereas, load cells ofthe beams 18, 24 measure the force being applied to the other lateralside of the load transducer 10. The various moments are determined bysubtracting the sum total of the forces acting on one pair of load cellsfrom the sum total acting upon the opposite pair. For example,subtracting the sum total of the forces acting on load cell of beam 16and load cell of beam 18 from the sum total of the forces acting on loadcell of beam 24 and load cell of beam 26, subtracting the sum total ofload cells of beams 18, 24 from the sum total of load cells of beams 16,26.

The sensory information from the strain gages 34, 36, 38 is transmittedto a microprocessor which could then be used to control the assembly towhich the load transducer is a part of such as a robotic assembly. Asbest shown in FIG. 1 , the planar central body portion 14 of thetransducer frame 12 provides an area where associated electronics and/orcircuitry can be mounted. Alternatively, the electronics and/orcircuitry can be mounted at any other suitable location. FIG. 5schematically illustrates exemplary electronic components that can beincluded in the load transducer data processing system. The strain gages34, 36, 38 of load transducer 10 may be electrically connected to asignal amplifier/converter 40, which in turn, is electrically connectedto a computer 42 (i.e., a data acquisition and processing device or adata processing device with a microprocessor). The components 10, 40, 42of the system may be connected either by wiring, or wirelessly to oneanother.

FIG. 5 graphically illustrates the acquisition and processing of theload data carried out by the exemplary load transducer data processingsystem. Initially, as shown in FIG. 5 , external forces F1-F4 and/ormoments are applied to the load transducer 10. When the electricalresistance of each strain gage 34, 36, 38 is altered by the applicationof the applied forces and/or moments, the change in the electricalresistance of the strain gages brings about a consequential change inthe output voltage of the strain gage bridge circuit (e.g., a Wheatstonebridge circuit). Thus, in one embodiment, the eight (8) strain gages 34,36, 38 output a total of eight (8) analog output voltages (signals). Insome embodiments, the eight (8) analog output voltages from the eight(8) strain gages 34, 36, 38 are then transmitted to a preamplifier board(not shown) for preconditioning. The preamplifier board is used toincrease the magnitudes of the analog voltage signals, and preferably,to convert the analog voltage signals into digital voltage signals aswell. After which, the load transducer 10 transmits the output signalsS_(TO1)-S_(TO8) to a main signal amplifier/converter 40. Depending onwhether the preamplifier board also includes an analog-to-digital (A/D)converter, the output signals S_(TO1)-S_(TO8) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 40 further magnifies the transducer output signalsS_(TO1)-S_(TO8), and if the signals S_(TO1)-S_(TO8) are of theanalog-type (for a case where the preamplifier board did not include ananalog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 40transmits either the digital or analog signals S_(ACO1)-S_(ACO8) to thedata acquisition/data processing device 42 (computer 42) so that theforces and/or moments that are being applied to the load transducer 10can be transformed into output load values OL. The computer or dataacquisition/data processing device 42 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(ACO8) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor of the computer 42.

When the computer or data acquisition/data processing device 42 receivesthe voltage signals S_(ACO1)-S_(ACO8), it initially transforms thesignals into output forces and/or moments by multiplying the voltagesignals S_(ACO1)-S_(ACO8) by a calibration matrix. After which, theforce components F_(X), F_(Y), F_(Z) and the moment components M_(X),M_(Y), M_(Z) applied to the load transducer 10 are determined by thecomputer or data acquisition/data processing device 42. Also, the centerof pressure (i.e., the x and y coordinates of the point of applicationof the force applied to the load transducer 10) can be determined by thecomputer or data acquisition/data processing device 42.

FIGS. 6-9 illustrate a load transducer 10′ according to a secondexemplary embodiment of the present invention. With reference to thesefigures, it can be seen that, in some respects, the second exemplaryembodiment is similar to that of the first embodiment. Moreover, someparts are common to both such embodiments. For the sake of brevity, theparts that the second embodiment of the load transducer has in commonwith the first embodiment will only be briefly mentioned, if at all,because these components have already been explained in detail above.Furthermore, in the interest of clarity, these components will bedenoted using the same reference characters that were used in the firstembodiment.

Initially, referring to the perspective view of FIG. 6 , it can be seenthat, like the first exemplary embodiment, the transducer frame 12′ ofthe second embodiment includes a central body portion 14 and a pluralityof beams 16, 18, 20′, 24′, 28, 30 extending outwardly therefrom.Although, unlike the first exemplary embodiment of the load transducer,the side 14 b of the body portion 14 of the load transducer 10′ containsonly a single beam 20′ extending therefrom, rather two beams 20, 22 (seeFIG. 1 ). Similarly, unlike the load transducer 10 of the firstembodiment, the side 14 c of the body portion 14 of the load transducer10′ contains only a single beam 24′ extending therefrom, rather twobeams 24, 26 (refer to FIG. 1 ). Also, unlike the load transducer 10 ofthe first embodiment, the load transducer 10′ includes only three straingages 34 that are sensitive to the vertical force component (i.e., threeF_(Z) strain gages), rather than four strain gages.

In particular, in the second embodiment, beams 16, 18, 24′ each comprisea strain gage 34 disposed on the top surface thereof that is sensitiveto the vertical force component (i.e., a F_(z) strain gage). Beams 18,24′ also each comprise a strain gage 36 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(x) strain gage), while beams 20′, 30 each comprise a strain gage 38disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(Y) strain gage). The load transducer 10′ ofthe second embodiment is capable of measuring the three force components(F_(X), F_(Y), F_(Z)) and the three moment components (M_(X), M_(Y),M_(Z)) with a minimum of six beams 16, 18, 20′, 24′, 28, 30 (i.e., threeinput beams and three output beams) and a minimum of seven strain gages34, 36, 38.

Now, with reference to the top view illustrated in FIG. 9 , it can beseen that the central longitudinal axis LA5 of the beam 20′, whichextends from side 14 b of the body portion 14, is generally equallyspaced apart from the central longitudinal axis LA3 and LA4 (i.e., thecentral longitudinal axis LA5 of the beam 20′ is generally centeredbetween the central longitudinal axis LA3 of beam 30 and the centrallongitudinal axis LA4 of beam 28). Similarly, as shown in FIG. 9 , thelongitudinal axis LA6 of the beam 24′, which extends from side 14 c ofthe body portion 14, is generally equally spaced apart from the centrallongitudinal axis LA1 and LA2 (i.e., the central longitudinal axis LA6of the beam 24′ is generally centered between the central longitudinalaxis LA1 of beam 16 and the central longitudinal axis LA2 of beam 18).The other features of the load transducer 10′ are similar to that of theload transducer 10, and thus, need not be reiterated herein.

FIGS. 10-14 illustrate a load transducer 100 according to a thirdexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 10 , it can be seen that the loadtransducer 100 generally includes a one-piece compact transducer frame112 having a central body portion 114 and a plurality of generallyU-shaped transducer beams 116, 118, 120, 122 extending outwardly fromthe central body portion 114. As best illustrated in FIG. 10 , each ofthe beams 116, 118, 120, 122 comprises a plurality of load cells ortransducer elements for measuring forces and/or moments.

With reference again to FIG. 10 , it can be seen that the illustratedcentral body portion 114 is generally in the form of square band-shapedelement with a central opening 102 disposed therethrough. In FIG. 10 ,it can be seen that the body portion 114 comprises a first pair ofopposed sides 114 a, 114 c and a second pair of opposed sides 114 b, 114d. The side 114 a is disposed generally parallel to the side 114 c,while the side 114 b is disposed generally parallel to the side 114 d.Each of the sides 114 a, 114 b, 114 c, 114 d is disposed generallyperpendicular to the planar top and bottom surfaces of the body portion114. Also, each of the first pair of opposed sides 114 a, 114 c isdisposed generally perpendicular to each of the second pair of opposedsides 114 b, 114 d. In addition, as shown in FIG. 10 , each of theopposed sides 114 a, 114 c comprises a beam connecting portion 128extending outward therefrom. In the illustrated embodiment, it can beseen that each of the beam connecting portions 128 comprises a pluralityof apertures 130 (e.g., two apertures 130) disposed therethrough foraccommodating fasteners (e.g., screws) that attach the load transducer100 to another object, such as a robotic arm, etc. Also, as depicted inthe side views of FIGS. 11 and 12 and the bottom view of FIG. 14 , thebottom surface of the central body portion 114 comprises a raisedportion or standoff portion 126 for elevating the transducer beams 116,118, 120, 122 above the object (e.g., robotic arm) to which the loadtransducer 100 is attached so that forces and/or moments are capable ofbeing accurately measured by the load transducer 100. In one or moreembodiments, the structural components to which the load transducer 100is mounted are connected only to the top standoff portions 124 and thebottom standoff 126 so as to ensure that the total load applied to theload transducer 100 is transmitted through the transducer beams 116,118, 120, 122.

As shown in FIGS. 10-14 , the illustrated generally U-shaped transducerbeams 116, 118, 120, 122 are each attached to one of the sides 114 a,114 b, 114 c, 114 d of the body portion 114 via a connecting portion128, and extend generally horizontally outward therefrom. In particular,beams 116, 118 extend generally horizontally outward from opposed sidesof the beam connecting portion 128 attached to side 114 a of the bodyportion 114, while the beams 120, 122 extend generally horizontallyoutward from opposed sides of the beam connecting portion 128 attachedto side 114 c of the body portion 114. As best shown in FIG. 10 , thetop and bottom surfaces of each of the illustrated beams 116, 118, 120,122 are disposed substantially co-planar with the top and bottomsurfaces of the body portion 114. Each of the illustrated beams 116,118, 120, 122 has a U-shaped cantilevered end relative to the bodyportion 114 that allows for deflection of the ends of the beams inmultiple directions.

With particular reference to FIGS. 10, 13, and 14 , it can be seen thateach of the generally U-shaped beams 116, 118, 120, 122 comprises aplurality of segmental beam portions, wherein each of the successivebeam portions are disposed substantially perpendicular to theimmediately preceding beam portion. For example, as shown in FIG. 10 ,the first generally U-shaped transducer beam 116 comprises a first beamportion 116 a extending from a first side of the beam connecting portion128, a second beam portion 116 b connected to the first beam portion 116a and disposed substantially perpendicular thereto, a third beam portion116 c connected to the second beam portion 116 b and disposedsubstantially perpendicular thereto, and a fourth beam portion 116 dconnected to the third beam portion 116 c and disposed substantiallyperpendicular thereto. Similarly, the second generally U-shapedtransducer beam 118 comprises a first beam portion 118 a extending froma second side of the beam connecting portion 128 (which is generallyopposite to the first side of the beam connecting portion 128 from whichthe first beam portion 116 a extends), a second beam portion 118 bconnected to the first beam portion 118 a and disposed substantiallyperpendicular thereto, a third beam portion 118 c connected to thesecond beam portion 118 b and disposed substantially perpendicularthereto, and a fourth beam portion 118 d connected to the third beamportion 118 c and disposed substantially perpendicular thereto. Withreference to FIGS. 10, 13, and 14 , it can be seen that the generallyU-shaped transducer beams 120, 122 are generally mirror images of thegenerally U-shaped transducer beams 116, 118, and thus, have the samestructure as the generally U-shaped transducer beams 116, 118. Referringagain to FIGS. 10, 13, and 14 , it can be seen that the fourth beamportion of each of the generally U-shaped transducer beams 116, 118,120, 122 comprises a raised portion or standoff portion 124 withmounting apertures 132 (e.g., two apertures 132) disposed therethroughfor accommodating fasteners (e.g., screws) that attach the loadtransducer 100 to another object, such as a robotic arm, etc. Inaddition, as shown in FIGS. 10 and 13 , each generally U-shapedtransducer beam 116, 118, 120, 122 comprises a central beam gap 106,which is bounded by the second, third, and fourth beam portions. Also,it can be seen that the first and second beam portions of eachtransducer beam 116, 118, 120, 122 are separated from the opposing sidesof the central body portion 114 by an L-shaped gap 104. That is, thesides of the central body portion 114, which face the sides of the firstand second beam portions in an opposing relationship, are separated fromthe sides of the first and second beam portions by the L-shaped gap 104.

As best shown in the perspective view of FIG. 10 , the illustrated loadcells are located on the transducer beams 116, 118, 120, 122. In theillustrated embodiment, each load cell comprises a plurality of straingages 134, 136, 138. Specifically, in the illustrated embodiment, eachof the first portions (e.g., 116 a, 118 a) of the transducer beams 116,118, 120, 122 comprise a strain gage 134 disposed on the top surfacethereof that is sensitive to the vertical force component (i.e., a F_(Z)strain gage). The first portions (e.g., 116 a, 118 a) of the transducerbeams 116, 118, 120, 122 also each comprise a strain gage 138 disposedon a side surface thereof that is sensitive to a first shear forcecomponent (i.e., a F_(Y) strain gage). Also, in the illustratedembodiment, each of the fourth portions (e.g., 116 d, 118 d) of thetransducer beams 116, 118, 120, 122 comprise a strain gage 136 disposedon a side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(X) strain gage).

As best shown in FIG. 10 , the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 134, 136, 138 aremounted to either top or side surfaces of the beams 116, 118, 120, 122between their attachment locations to the beam connecting portions 128and the raised end portions 124 thereof. Alternatively, the strain gages134 can be mounted to the bottom surfaces of the first beam portions(e.g., 116 a, 118 a) of the transducer beams 116, 118, 120, 122, whilethe strain gages 138 can be mounted to the opposite side surfaces of thefirst beam portions (e.g., 116 a, 118 a) of the transducer beams 116,118, 120, 122. Similarly, the strain gages 136 can be mounted to theopposite side surfaces of the fourth beam portions (e.g., 116 d, 118 d)of the transducer beams 116, 118, 120, 122. In general, the strain gages134, 136, 138 are mounted to surfaces generally normal to the directionof applied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). Itis also noted that alternatively, the strain gages 134 can be mounted atboth the top surface and the bottom surface of the first beam portionsof the beams 116, 118, 120, 122, the strain gages 138 can be mounted atboth opposed side surfaces of first beam portions of the beams 116, 118,120, 122, and/or the strain gages 136 can be mounted at both opposedside surfaces of the beams 116, 118, 120, 122. These strain gages 134,136, 138 measure force either by bending moment or difference of bendingmoments at two cross sections. As force is applied to the ends of thebeams, the beams 116, 118, 120, 122 bend. This bending either stretchesor compresses the strain gages 134, 136, 138, which in turn changes theresistance of the electrical current passing therethrough. The amount ofchange in the electrical voltage or current is proportional to themagnitude of the applied force, as applied to the ends of respectivebeams 116, 118, 120, 122.

Next, referring to FIGS. 15-18 , a load transducer 200 according to afourth exemplary embodiment of the present invention will be described.Referring initially to the perspective view of FIG. 15 , it can be seenthat the load transducer 200 generally includes a one-piece compacttransducer frame 204 that is generally in the form of square band-shapedelement with a central opening 202 disposed therethrough. As bestillustrated in FIGS. 15 and 18 , the square band-shaped transducer frame204 comprises a first transducer beam side portion 206, a secondtransducer beam side portion 208, a third transducer beam side portion210, and a fourth transducer beam side portion 212. Also, as shown inFIG. 15 , the transducer beam side portions 206, 208, 210, 212 comprisea plurality of load cells or transducer elements for measuring forcesand/or moments. The transducer frame 204 of the load transducer 200 issimilar to the other transducers (e.g., transducers 300, 400) that willbe described hereinafter, except that the central body portion of thesetransducers (e.g., 300, 400) has been removed in the load transducer200.

As shown in FIGS. 15-18 , the illustrated transducer beam side portions206, 208, 210, 212 of the transducer frame 204 are arranged in agenerally square configuration. In particular, with reference to FIGS.15 and 18 , the first transducer beam side portion 206 is connected tothe second transducer beam side portion 208 on one of its longitudinalends, and the fourth transducer beam side portion 212 on the other oneof its longitudinal ends, and the first transducer beam side portion 206is disposed generally perpendicular to each of the second and fourthtransducer beam side portions 208, 212. The second transducer beam sideportion 208 is connected to the first transducer beam side portion 206on one of its longitudinal ends, and the third transducer beam sideportion 210 on the other one of its longitudinal ends, and the secondtransducer beam side portion 208 is disposed generally perpendicular toeach of the first and third transducer beam side portions 206, 210. Thethird transducer beam side portion 210 is connected to the secondtransducer beam side portion 208 on one of its longitudinal ends, andthe fourth transducer beam side portion 212 on the other one of itslongitudinal ends, and the third transducer beam side portion 210 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 208, 212. The fourth transducer beam sideportion 212 is connected to the third transducer beam side portion 210on one of its longitudinal ends, and the first transducer beam sideportion 206 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 212 is disposed generally perpendicular toeach of the first and third transducer beam side portions 206, 210.Referring to FIGS. 15, 17, and 18 , it can be seen that the top surfaceof the second transducer beam side portion 208 and the top surface ofthe fourth transducer beam side portion 212 each comprises a centralraised portion or standoff portion 214 with spaced apart mountingapertures 218 (e.g., two spaced apart apertures 218) disposedtherethrough for accommodating fasteners (e.g., screws) that attach theload transducer 200 to another object, such as a robotic arm, etc.Similarly, with reference to FIGS. 15 and 16 , it can be seen that thebottom surface of the first transducer beam side portion 206 and thebottom surface of the third transducer beam side portion 210 eachcomprises a central raised portion or standoff portion 216 with spacedapart mounting apertures 218 (e.g., two spaced apart apertures 218)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 200 to another object, such as a robotic arm,etc.

As best shown in the perspective view of FIG. 15 , the illustrated loadcells are located on the transducer beam side portions 206, 208, 210,212. In the illustrated embodiment, each load cell comprises one or morestrain gages 220, 222, 224. Specifically, in the illustrated embodiment,the first transducer beam side portion 206 and the third transducer beamside portion 210 each comprise a plurality of spaced apart strain gages220 (e.g., two spaced apart strain gages 220) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 208 andthe fourth transducer beam side portion 212 also each comprise aplurality of spaced apart strain gages 222 (e.g., two spaced apartstrain gages 222) disposed on a side surface thereof that is sensitiveto a first shear force component (i.e., a F_(X) strain gage). Also, inthe illustrated embodiment, the first transducer beam side portion 206and the third transducer beam side portion 210 also each comprise aplurality of spaced apart strain gages 224 (e.g., two spaced apartstrain gages 224) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

As best shown in FIG. 15 , the illustrated load cells are configured asbending beam load cells. The illustrated strain gages 220, 222, 224 aremounted to either top or side surfaces of the transducer beam sideportions 206, 208, 210, 212 between the opposed longitudinal endsthereof. Alternatively, the strain gages 220 can be mounted to thebottom surfaces of the first and third transducer beam side portions206, 210, while the strain gages 222 can be mounted to the opposite sidesurfaces of the second and fourth transducer beam side portions 208,212. Similarly, the strain gages 224 can be mounted to the opposite sidesurfaces of the first and third transducer beam side portions 206, 210.In general, the strain gages 220, 222, 224 are mounted to surfacesgenerally normal to the direction of applied vertical and/or shearforces (i.e., F_(X), F_(Y), F_(Z)). It is also noted that alternatively,the strain gages 220 can be mounted at both the top surface and thebottom surface of the first and third transducer beam side portions 206,210, the strain gages 222 can be mounted at both opposed side surfacesof second and fourth transducer beam side portions 208, 212, and/or thestrain gages 224 can be mounted at both opposed side surfaces of thefirst and third transducer beam side portions 206, 210. These straingages 220, 222, 224 measure force either by bending moment or differenceof bending moments at two cross sections. As force is applied to thebeams, the beams 206, 208, 210, 212 bend. This bending either stretchesor compresses the strain gages 220, 222, 224, which in turn changes theresistance of the electrical current passing therethrough. The amount ofchange in the electrical voltage or current is proportional to themagnitude of the applied force, as transferred through the end portionsof respective beams 206, 208, 210, 212.

An exemplary mounting arrangement for the load transducer 200 isillustrated in FIG. 25 . As depicted in the perspective view of FIG. 25, the load transducer 200 is mounted between a top plate member 226 anda bottom plate member 228. Specifically, in this mounting arrangement,the bottom surface 226 a of the top plate member 226 abuts the topsurfaces of the standoff portions 214 on the second and fourthtransducer beam side portions 208, 212, while the top surface 228 a ofthe bottom plate member 228 abuts the bottom surfaces of the standoffportions 216 on the first and third transducer beam side portions 206,210. As such, in this mounting arrangement, an upper gap 230 is formedbetween the top surfaces of the load transducer 200 and the bottomsurface 226 a of the top plate member 226 by the two spaced apart topstandoff portions 214. Similarly, a lower gap 232 is formed between thebottom surfaces of the load transducer 200 and the top surface 228 a ofthe bottom plate member 228 by the two spaced apart bottom standoffportions 216. Thus, as result of the mounting arrangement illustrated inFIG. 25 , the entire load exerted on the load transducer 200 by the topand bottom plate members 226, 228 is transferred through the cornerportions of the transducer frame 204, which are instrumented with thestrain gages 220, 222, 224 and are spaced apart from the top and bottomplate members 226, 228 by the standoff portions 214, 216.

While the exemplary mounting arrangement is illustrated in FIG. 25 usingthe load transducer 200, it is to be understood that each of the otherload transducers 10, 10′, 100, 300, 400, 500, 600, 700, 800 describedherein are mounted in generally the same manner to adjoining structures(e.g., plate members 226, 228 or components of a robotic arm). That is,the standoff portions described on the load transducers 10, 10′, 100,300, 400, 500, 600, 700, 800 perform the same functions as thosedescribed in conjunction with the load transducer 200 above. Inparticular, the adjoining structures to which the transducers aremounted are only connected to the top standoff portions and the bottomstandoff portions of each load transducer 10, 10′, 100, 300, 400, 500,600, 700, 800 so as to ensure that the total loads applied to the loadtransducers 10, 10′, 100, 300, 400, 500, 600, 700, 800 are transmittedthrough the instrumented portions of the transducer beams of thetransducers.

FIG. 19 illustrates a load transducer 300 according to a fifth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the fifth exemplary embodiment issimilar to that of the fourth embodiment. Moreover, some parts arecommon to both such embodiments. For the sake of brevity, the parts thatthe fifth embodiment of the load transducer has in common with thefourth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 19 , it can be seenthat, unlike the fourth exemplary embodiment of the load transducer, theload transducer 300 comprises a central body portion 302. Also, unlikethe load transducer 200 of the fourth embodiment, the second and fourthtransducer beam side portions 308, 312 have side projecting portions 326extending from the inner sides thereof towards the central body portion302. As shown in FIG. 19 , the load transducer 300 generally includes aone-piece compact transducer frame 304 with a central body portion 302and a plurality of transducer beam side portions 306, 308, 310, 312.

With reference again to FIG. 19 , it can be seen that the illustratedcentral body portion 302 is generally in the form of rectangularband-shaped element with a central opening 303 disposed therethrough. InFIG. 19 , it can be seen that the body portion 302 comprises a firstpair of opposed side portions 302 a, 302 c and a second pair of opposedside portions 302 b, 302 d. The side portion 302 a is disposed generallyparallel to the side portion 302 c, while the side portion 302 b isdisposed generally parallel to the side portion 302 d. Each of the sidesurfaces of the side portions 302 a, 302 b, 302 c, 302 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 302 a, 302 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 302 b, 302 d. In addition, as shown in FIG. 19 , each ofthe opposed side portions 302 a, 302 c forms a middle portion of thefirst and third transducer beam side portions 306, 310. In theillustrated embodiment, it can be seen that each of the opposed sideportions 302 a, 302 c comprises a plurality of apertures 318 (e.g., twoapertures 318) disposed therethrough for accommodating fasteners (e.g.,screws) that attach the load transducer 300 to another object, such as arobotic arm, etc. Also, as depicted in the FIG. 19 , the central bodyportion 302 comprises a raised top portion or top standoff portion 314for spacing the transducer beam side portions 306, 308, 310, 312 apartfrom the object (e.g., robotic arm) to which the load transducer 300 isattached so that forces and/or moments are capable of being accuratelymeasured by the load transducer 300.

As shown in FIG. 19 , the illustrated transducer beam side portions 306,308, 310, 312 of the transducer frame 304 are arranged in a generallysquare configuration. In particular, with reference to FIG. 19 , thefirst transducer beam side portion 306 is connected to the secondtransducer beam side portion 308 on one of its longitudinal ends, andthe fourth transducer beam side portion 312 on the other one of itslongitudinal ends, and the first transducer beam side portion 306 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 308, 312. The second transducer beam sideportion 308 is connected to the first transducer beam side portion 306on one of its longitudinal ends, and the third transducer beam sideportion 310 on the other one of its longitudinal ends, and the secondtransducer beam side portion 308 is disposed generally perpendicular toeach of the first and third transducer beam side portions 306, 310. Thethird transducer beam side portion 310 is connected to the secondtransducer beam side portion 308 on one of its longitudinal ends, andthe fourth transducer beam side portion 312 on the other one of itslongitudinal ends, and the third transducer beam side portion 310 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 308, 312. The fourth transducer beam sideportion 312 is connected to the third transducer beam side portion 310on one of its longitudinal ends, and the first transducer beam sideportion 306 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 312 is disposed generally perpendicular toeach of the first and third transducer beam side portions 306, 310.Referring to FIG. 19 , it can be seen that the bottom surface of thesecond transducer beam side portion 308 and the bottom surface of thefourth transducer beam side portion 312 each comprises a centralstandoff portion 316, which is connected to the side projecting portion326 on each of the transducer beam side portions 308, 312. The sideprojecting portions 326 each comprise spaced apart mounting apertures328 (e.g., two spaced apart apertures 328) disposed therethrough foraccommodating fasteners (e.g., screws) that attach the load transducer300 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 19 , the illustrated loadcells are located on the transducer beam side portions 306, 308, 310,312. In the illustrated embodiment, each load cell comprises one or morestrain gages 320, 322, 324. Specifically, in the illustrated embodiment,the second transducer beam side portion 308 and the fourth transducerbeam side portion 312 each comprise a plurality of spaced apart straingages 320 (e.g., two spaced apart strain gages 320) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 308 andfourth transducer beam side portion 312 also each comprise a pluralityof spaced apart strain gages 322 (e.g., two spaced apart strain gages322) disposed on a side surface thereof that is sensitive to a firstshear force component (i.e., a F_(X) strain gage). Also, in theillustrated embodiment, the first transducer beam side portion 306 andthe third transducer beam side portion 310 also each comprise aplurality of spaced apart strain gages 324 (e.g., two spaced apartstrain gages 324) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

FIG. 20 illustrates a load transducer 400 according to a sixth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the sixth exemplary embodiment issimilar to that of the fifth embodiment. Moreover, some parts are commonto both such embodiments. For the sake of brevity, the parts that thesixth embodiment of the load transducer has in common with the fifthembodiment will only be briefly mentioned because these components havealready been explained in detail above.

Initially, referring to the perspective view of FIG. 20 , it can be seenthat, unlike the fifth exemplary embodiment of the load transducer, allfour sides of the central body portion 402 of the load transducer 400are spaced apart from the transducer beam side portions 406, 408, 410,412. In particular, the central body portion 402 is spaced apart fromthe transducer beam side portions 406, 408, 410, 412 by the two C-shapedgaps 426. Also, unlike the load transducer 300 of the fifth embodiment,the first and third transducer beam side portions 406, 410 of the loadtransducer 400 are connected to the central body portion 402 by the beamconnecting portions 417. Although, like the load transducer 300, theload transducer 400 generally includes a one-piece compact transducerframe 404 with a central body portion 402 and a plurality of transducerbeam side portions 406, 408, 410, 412.

With reference again to FIG. 20 , it can be seen that the illustratedcentral body portion 402 is generally in the form of rectangularband-shaped element with a central opening 403 disposed therethrough. InFIG. 20 , it can be seen that the body portion 402 comprises a firstpair of opposed side portions 402 a, 402 c and a second pair of opposedside portions 402 b, 402 d. The side portion 402 a is disposed generallyparallel to the side portion 402 c, while the side portion 402 b isdisposed generally parallel to the side portion 402 d. Each of the sidesurfaces of the side portions 402 a, 402 b, 402 c, 402 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 402 a, 402 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 402 b, 402 d. In addition, as shown in FIG. 20 , each ofthe opposed side portions 402 a, 402 c is connected to the first andthird transducer beam side portions 406, 410 by beam connecting portions417. In the illustrated embodiment, it can be seen that each of the beamconnecting portions 417 comprises a plurality of apertures 418 (e.g.,two apertures 418) disposed therethrough for accommodating fasteners(e.g., screws) that attach the load transducer 400 to another object,such as a robotic arm, etc.

As shown in FIG. 20 , the illustrated transducer beam side portions 406,408, 410, 412 of the transducer frame 404 are arranged in a generallysquare configuration. In particular, with reference to FIG. 20 , thefirst transducer beam side portion 406 is connected to the secondtransducer beam side portion 408 on one of its longitudinal ends, andthe fourth transducer beam side portion 412 on the other one of itslongitudinal ends, and the first transducer beam side portion 406 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 408, 412. The second transducer beam sideportion 408 is connected to the first transducer beam side portion 406on one of its longitudinal ends, and the third transducer beam sideportion 410 on the other one of its longitudinal ends, and the secondtransducer beam side portion 408 is disposed generally perpendicular toeach of the first and third transducer beam side portions 406, 410. Thethird transducer beam side portion 410 is connected to the secondtransducer beam side portion 408 on one of its longitudinal ends, andthe fourth transducer beam side portion 412 on the other one of itslongitudinal ends, and the third transducer beam side portion 410 isdisposed generally perpendicular to each of the second and fourthtransducer beam side portions 408, 412. The fourth transducer beam sideportion 412 is connected to the third transducer beam side portion 410on one of its longitudinal ends, and the first transducer beam sideportion 406 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 412 is disposed generally perpendicular toeach of the first and third transducer beam side portions 406, 410.Referring to FIG. 20 , it can be seen that the top surface of the secondtransducer beam side portion 408 and the top surface of the fourthtransducer beam side portion 412 each comprises a central raised portionor standoff portion 414 with spaced apart mounting apertures 428 (e.g.,two spaced apart apertures 428) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 400 to anotherobject, such as a robotic arm, etc. Similarly, with reference to FIG. 20, it can be seen that the bottom surface of the first transducer beamside portion 406 and the bottom surface of the third transducer beamside portion 410 each comprises a central raised portion or standoffportion 416.

As best shown in the perspective view of FIG. 20 , the illustrated loadcells are located on the transducer beam side portions 406, 408, 410,412. In the illustrated embodiment, each load cell comprises one or morestrain gages 420, 422, 424. Specifically, in the illustrated embodiment,the first transducer beam side portion 406 and the third transducer beamside portion 410 each comprise a plurality of spaced apart strain gages420 (e.g., two spaced apart strain gages 420) disposed on the topsurface thereof that is sensitive to the vertical force component (i.e.,a F_(Z) strain gage). The second transducer beam side portion 408 andfourth transducer beam side portion 412 also each comprise a pluralityof spaced apart strain gages 422 (e.g., two spaced apart strain gages422) disposed on a side surface thereof that is sensitive to a firstshear force component (i.e., a F_(X) strain gage). Also, in theillustrated embodiment, the first transducer beam side portion 406 andthe third transducer beam side portion 410 also each comprise aplurality of spaced apart strain gages 424 (e.g., two spaced apartstrain gages 424) disposed on a side surface thereof that is sensitiveto a second shear force component (i.e., a F_(Y) strain gage).

FIG. 21 illustrates a load transducer 500 according to a seventhexemplary embodiment of the present invention. With reference to thisfigure, it can be seen that, in some respects, the seventh exemplaryembodiment is similar to that of the fifth embodiment. Moreover, someparts are common to both such embodiments. For the sake of brevity, theparts that the seventh embodiment of the load transducer has in commonwith the fifth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 21 , it can be seenthat, like the fifth embodiment described above, the load transducer 500generally includes a one-piece compact transducer frame 504 with acentral body portion 502 and a plurality of transducer beam sideportions 506, 508, 510, 512, 514, 516. Although, the central bodyportion 502 of the load transducer 500 is considerably wider than thecentral body portion 302 of the load transducer 300.

With reference again to FIG. 21 , it can be seen that the illustratedcentral body portion 502 is generally in the form of square band-shapedelement with a central opening 530 disposed therethrough. In FIG. 21 ,it can be seen that the body portion 502 comprises a first pair ofopposed side portions 502 a, 502 c and a second pair of opposed sideportions 502 b, 502 d. The side portion 502 a is disposed generallyparallel to the side portion 502 c, while the side portion 502 b isdisposed generally parallel to the side portion 502 d. Each of the sidesurfaces of the side portions 502 a, 502 b, 502 c, 502 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 502 a, 502 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 502 b, 502 d. In addition, as shown in FIG. 21 , each ofthe opposed side portions 502 a, 502 c is disposed between a respectivepair of transducer beam side portions 506, 508 and 512, 514. In theillustrated embodiment, it can be seen that each of the opposed sideportions 502 a, 502 c comprises a plurality of apertures 532 (e.g., twoapertures 532) disposed therethrough for accommodating fasteners (e.g.,screws) that attach the load transducer 500 to another object, such as arobotic arm, etc. Also, as depicted in the FIG. 21 , the central bodyportion 502 comprises a raised bottom portion or bottom standoff portion520 for spacing the transducer beam side portions 506, 508, 510, 512,514, 516 apart from the object (e.g., robotic arm) to which the loadtransducer 500 is attached so that forces and/or moments are capable ofbeing accurately measured by the load transducer 500.

As shown in FIG. 21 , the first set of illustrated transducer beam sideportions 506, 514, 516 of the transducer frame 504 are arranged in agenerally C-shaped configuration on a first side of the central bodyportion 502. A first side aperture 534 is formed between the sideportion 502 d of the central body portion 502 and the first set oftransducer beam side portions 506, 514, 516. Referring again to FIG. 21, it can be seen that the first transducer beam side portion 506 isconnected to the sixth transducer beam side portion 516 on one of itslongitudinal ends, and the side portion 502 d of the central bodyportion 502 on the other one of its longitudinal ends, and the firsttransducer beam side portion 506 is disposed generally perpendicular tothe side portion 502 d of the central body portion 502 and to sixthtransducer beam side portion 516. Similarly, the fifth transducer beamside portion 514 is connected to the sixth transducer beam side portion516 on one of its longitudinal ends, and the side portion 502 d of thecentral body portion 502 on the other one of its longitudinal ends, andthe fifth transducer beam side portion 514 is disposed generallyperpendicular to the side portion 502 d of the central body portion 502and to sixth transducer beam side portion 516. The sixth transducer beamside portion 516 is connected to the first transducer beam side portion506 on one of its longitudinal ends, and the fifth transducer beam sideportion 514 on the other one of its longitudinal ends, and the sixthtransducer beam side portion 516 is disposed generally perpendicular toeach of the first and fifth transducer beam side portions 506, 514.Turning again to FIG. 21 , it can be seen that the second set oftransducer beam side portions 508, 510, 512 of the transducer frame 504is arranged in a generally C-shaped configuration on a second side ofthe central body portion 502, which is opposite to the first side of thecentral body portion 502. A second side aperture 534 is formed betweenthe side portion 502 b of the central body portion 502 and the secondset of transducer beam side portions 508, 510, 512. In FIG. 21 , it canbe seen that the second transducer beam side portion 508 is connected tothe third transducer beam side portion 510 on one of its longitudinalends, and the side portion 502 b of the central body portion 502 on theother one of its longitudinal ends, and the second transducer beam sideportion 508 is disposed generally perpendicular to the side portion 502b of the central body portion 502 and to third transducer beam sideportion 510. Similarly, the fourth transducer beam side portion 512 isconnected to the third transducer beam side portion 510 on one of itslongitudinal ends, and the side portion 502 b of the central bodyportion 502 on the other one of its longitudinal ends, and the fourthtransducer beam side portion 512 is disposed generally perpendicular tothe side portion 502 b of the central body portion 502 and to thirdtransducer beam side portion 510. The third transducer beam side portion510 is connected to the second transducer beam side portion 508 on oneof its longitudinal ends, and the fourth transducer beam side portion512 on the other one of its longitudinal ends, and the third transducerbeam side portion 510 is disposed generally perpendicular to each of thesecond and fourth transducer beam side portions 508, 512. Also, as shownin FIG. 21 , it can be seen that the top surface of the third transducerbeam side portion 510 and the top surface of the sixth transducer beamside portion 516 each comprises a central standoff portion 518. Thecentral standoff portions 518 each comprise spaced apart mountingapertures 522 (e.g., two spaced apart apertures 522) disposedtherethrough for accommodating fasteners (e.g., screws) that attach theload transducer 500 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 21 , the illustrated loadcells are located on the transducer beam side portions 506, 508, 510,512, 514, 516. In the illustrated embodiment, each load cell comprisesone or more strain gages 524, 526, 528. Specifically, in the illustratedembodiment, the first transducer beam side portion 506, the secondtransducer beam side portion 508, the fourth transducer beam sideportion 512, and the fifth transducer beam side portion 514 eachcomprise a strain gage 524 disposed on the top surface thereof that issensitive to the vertical force component (i.e., a F_(Z) strain gage).The third transducer beam side portion 510 and the sixth transducer beamside portion 516 also each comprise a plurality of spaced apart straingages 526 (e.g., two spaced apart strain gages 526) disposed on a sidesurface thereof that is sensitive to a first shear force component(i.e., a F_(X) strain gage). Also, in the illustrated embodiment, thefirst transducer beam side portion 506, the second transducer beam sideportion 508, the fourth transducer beam side portion 512, and the fifthtransducer beam side portion 514 each comprises a strain gage 528disposed on an outer side surface thereof that is sensitive to a secondshear force component (i.e., a F_(Y) strain gage).

FIG. 22 illustrates a load transducer 600 according to an eighthexemplary embodiment of the present invention. With reference to thisfigure, it can be seen that, in some respects, the eighth exemplaryembodiment is similar to that of the preceding embodiments. Moreover,some parts are common to all of the embodiments. For the sake ofbrevity, the parts that the eighth embodiment of the load transducer hasin common with the preceding embodiments will only be briefly mentionedbecause these components have already been explained in detail above.

Initially, referring to the perspective view of FIG. 22 , it can be seenthat, like the preceding embodiments described above, the loadtransducer 600 generally includes a one-piece compact transducer frame604 with a central body portion 602 and a plurality of transducer beams606, 608, 610, 612, 614, 616 connected thereto. Although, the transducerbeams 606, 608, 610, 612, 614, 616 are arranged in a differentconfiguration than that which was described for the precedingembodiments.

With reference again to FIG. 22 , it can be seen that the illustratedcentral body portion 602 is generally in the form of square band-shapedelement with a central opening 630 disposed therethrough. In FIG. 22 ,it can be seen that the body portion 602 comprises a first pair ofopposed side portions 602 a, 602 c and a second pair of opposed sideportions 602 b, 602 d. The side portion 602 a is disposed generallyparallel to the side portion 602 c, while the side portion 602 b isdisposed generally parallel to the side portion 602 d. Each of the sidesurfaces of the side portions 602 a, 602 b, 602 c, 602 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 602 a, 602 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 602 b, 602 d. In addition, as shown in FIG. 22 , each ofthe opposed side portions 602 b, 602 d is connected to a respective setof transducer beams 606, 608, 610 and 612, 614, 616. In the illustratedembodiment, it can be seen that each of the opposed side portions 602 a,602 c comprises a plurality of apertures 632 (e.g., two apertures 632)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 600 to another object, such as a robotic arm,etc.

As shown in FIG. 22 , the first set of illustrated transducer beams 606,608, 610 of the transducer frame 604 is arranged in a generally T-shapedconfiguration on a first side of the central body portion 602. A firstside aperture 634 is formed between the side portion 602 d of thecentral body portion 602 and the first set of transducer beam sideportions 606, 608, 610. Referring again to FIG. 22 , it can be seen thatthe first transducer beam 606 is connected to the side portion 602 d ofthe central body portion 602 by means of two spaced apart connectingtransducer beams 608, 610. Specifically, the second transducer beam 608is connected to an inner side of the first transducer beam 606 on one ofits longitudinal ends, and the side portion 602 d of the central bodyportion 602 on the other one of its longitudinal ends, and the secondtransducer beam 608 is disposed generally perpendicular to the sideportion 602 d of the central body portion 602 and to first transducerbeam 606. Similarly, the third transducer beam 610 is connected to theinner side of the first transducer beam 606 on one of its longitudinalends, and the side portion 602 d of the central body portion 602 on theother one of its longitudinal ends, and the third transducer beam 610 isdisposed generally perpendicular to the side portion 602 d of thecentral body portion 602 and to first transducer beam 606. Turning againto FIG. 22 , it can be seen that the second set of transducer beams 612,614, 616 of the transducer frame 604 is arranged in a generally T-shapedconfiguration on a second side of the central body portion 602, which isopposite to the first side of the central body portion 602. A secondside aperture 634 is formed between the side portion 602 b of thecentral body portion 602 and the second set of transducer beam sideportions 612, 614, 616. In FIG. 22 , similar to the first transducerbeam 606, it can be seen that the fourth transducer beam 612 isconnected to the side portion 602 b of the central body portion 602 bymeans of two spaced apart connecting transducer beams 614, 616.Specifically, the fifth transducer beam 614 is connected to an innerside of the fourth transducer beam 612 on one of its longitudinal ends,and the side portion 602 b of the central body portion 602 on the otherone of its longitudinal ends, and the fifth transducer beam 614 isdisposed generally perpendicular to the side portion 602 b of thecentral body portion 602 and to fourth transducer beam 612. Similarly,the sixth transducer beam 616 is connected to the inner side of thefourth transducer beam 612 on one of its longitudinal ends, and the sideportion 602 b of the central body portion 602 on the other one of itslongitudinal ends, and the sixth transducer beam 616 is disposedgenerally perpendicular to the side portion 602 b of the central bodyportion 602 and to fourth transducer beam 612. Also, as shown in FIG. 22, it can be seen that the bottom surface of the first transducer beam606 and the bottom surface of the fourth transducer beam 612 eachcomprises a central standoff portion 620. In addition, it can be seenthat the opposed longitudinal ends of the first transducer beam 606 andthe fourth transducer beam 612 are each provided with raised standoffportions 618. Each raised standoff portion 618 is provided with amounting aperture 622 disposed therethrough for accommodating arespective fastener (e.g., a screw) that attaches the load transducer600 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 22 , the illustrated loadcells are located on the transducer beams 606, 608, 610, 612, 614, 616.In the illustrated embodiment, each load cell comprises one or morestrain gages 624, 626, 628. Specifically, in the illustrated embodiment,the first transducer beam 606 and the fourth transducer beam 612 eachcomprise a pair of spaced apart strain gages 624 disposed on the topsurfaces thereof that are sensitive to the vertical force component(i.e., F_(Z) strain gages). In FIG. 22 , it can be seen that each of thestrain gages 624 is disposed near the raised standoff portions 618 atthe opposed ends of the beams 606, 612. Also, in the illustratedembodiment, the second transducer beam 608, the third transducer beam610, the fifth transducer beam 614, and the sixth transducer beam 616each comprise a strain gage 626 disposed on an outer side surfacethereof that is sensitive to a first shear force component (i.e., aF_(X) strain gage). The first transducer beam 606 and the fourthtransducer beam 612 also each comprise a plurality of spaced apartstrain gages 628 (e.g., two spaced apart strain gages 628) disposed onan outer side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(Y) strain gage).

FIG. 23 illustrates a load transducer 700 according to a ninth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the ninth exemplary embodiment issimilar to that of the eighth embodiment. Moreover, some parts arecommon to all of the embodiments. For the sake of brevity, the partsthat the ninth embodiment of the load transducer has in common with theeighth embodiment will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 23 , it can be seenthat, like the eighth embodiment described above, the load transducer700 generally includes a one-piece compact transducer frame 704 with acentral body portion 702 and a plurality of transducer beams 706, 708,710, 712, 714, 716 connected thereto. Although, each of connectingtransducer beams 708, 710, and each of connecting transducer beams 714,716, are spaced considerably further apart from one another as comparedto the connecting transducer beams 608, 610, 614, 616 of the loadtransducer 600 such that the connecting beams 708, 710, 714, 716 aregenerally axially aligned with the side portions 702 a, 702 c of thecentral body portion 702.

With reference again to FIG. 23 , it can be seen that the illustratedcentral body portion 702 is generally in the form of square band-shapedelement with a central opening 730 disposed therethrough. In FIG. 23 ,it can be seen that the body portion 702 comprises a first pair ofopposed side portions 702 a, 702 c and a second pair of opposed sideportions 702 b, 702 d. The side portion 702 a is disposed generallyparallel to the side portion 702 c, while the side portion 702 b isdisposed generally parallel to the side portion 702 d. Each of the sidesurfaces of the side portions 702 a, 702 b, 702 c, 702 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 702 a, 702 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 702 b, 702 d. In addition, as shown in FIG. 23 , each ofthe opposed side portions 702 b, 702 d is connected to a respective setof transducer beams 706, 708, 710 and 712, 714, 716. In the illustratedembodiment, it can be seen that each of the opposed side portions 702 a,702 c comprises a plurality of apertures 732 (e.g., two apertures 732)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 700 to another object, such as a robotic arm,etc. Also, as depicted in the FIG. 23 , the central body portion 702comprises a raised bottom portion or bottom standoff portion 720 forspacing the transducer beams 706, 708, 710, 712, 714, 716 apart from anobject (e.g., robotic arm) to which the load transducer 700 is attachedso that forces and/or moments are capable of being accurately measuredby the load transducer 700.

As shown in FIG. 23 , the first set of illustrated transducer beams 706,708, 710 of the transducer frame 704 is arranged in a generally T-shapedconfiguration on a first side of the central body portion 702 (with thewide base of the T-shaped arrangement being formed by the connectingbeam transducers 708, 710). A first side aperture 734 is formed betweenthe side portion 702 d of the central body portion 702 and the first setof transducer beam side portions 706, 708, 710. Referring again to FIG.23 , it can be seen that the first transducer beam 706 is connected tothe side portion 702 d of the central body portion 702 by means of twospaced apart connecting transducer beams 708, 710. Specifically, thesecond transducer beam 708 is connected to an inner side of the firsttransducer beam 706 on one of its longitudinal ends, and the sideportion 702 d of the central body portion 702 on the other one of itslongitudinal ends, and the second transducer beam 708 is disposedgenerally perpendicular to the side portion 702 d of the central bodyportion 702 and to first transducer beam 706. Similarly, the thirdtransducer beam 710 is connected to the inner side of the firsttransducer beam 706 on one of its longitudinal ends, and the sideportion 702 d of the central body portion 702 on the other one of itslongitudinal ends, and the third transducer beam 710 is disposedgenerally perpendicular to the side portion 702 d of the central bodyportion 702 and to first transducer beam 706. Turning again to FIG. 23 ,it can be seen that the second set of transducer beams 712, 714, 716 ofthe transducer frame 704 is arranged in a generally T-shapedconfiguration on a second side of the central body portion 702, which isopposite to the first side of the central body portion 702 (with thewide base of the T-shaped arrangement being formed by the connectingbeam transducers 714, 716). A second side aperture 734 is formed betweenthe side portion 702 b of the central body portion 702 and the secondset of transducer beam side portions 712, 714, 716. In FIG. 23 , similarto the first transducer beam 706, it can be seen that the fourthtransducer beam 712 is connected to the side portion 702 b of thecentral body portion 702 by means of two spaced apart connectingtransducer beams 714, 716. Specifically, the fifth transducer beam 714is connected to an inner side of the fourth transducer beam 712 on oneof its longitudinal ends, and the side portion 702 b of the central bodyportion 702 on the other one of its longitudinal ends, and the fifthtransducer beam 714 is disposed generally perpendicular to the sideportion 702 b of the central body portion 702 and to fourth transducerbeam 712. Similarly, the sixth transducer beam 716 is connected to theinner side of the fourth transducer beam 712 on one of its longitudinalends, and the side portion 702 b of the central body portion 702 on theother one of its longitudinal ends, and the sixth transducer beam 716 isdisposed generally perpendicular to the side portion 702 b of thecentral body portion 702 and to fourth transducer beam 712. Also, inFIG. 23 , it can be seen that the opposed longitudinal ends of the firsttransducer beam 706 and the fourth transducer beam 712 are each providedwith raised standoff portions 718. Each raised standoff portion 718 isprovided with a mounting aperture 722 disposed therethrough foraccommodating a respective fastener (e.g., a screw) that attaches theload transducer 700 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 23 , the illustrated loadcells are located on the transducer beams 706, 708, 710, 712, 714, 716.In the illustrated embodiment, each load cell comprises one or morestrain gages 724, 726, 728. Specifically, in the illustrated embodiment,the first transducer beam 706 and the fourth transducer beam 712 eachcomprise a pair of spaced apart strain gages 724 disposed on the topsurfaces thereof that are sensitive to the vertical force component(i.e., F_(Z) strain gages). In FIG. 23 , it can be seen that each of thestrain gages 724 is disposed near the raised standoff portions 718 atthe opposed ends of the beams 706, 712. Also, in the illustratedembodiment, the second transducer beam 708, the third transducer beam710, the fifth transducer beam 714, and the sixth transducer beam 716each comprise a strain gage 726 disposed on an outer side surfacethereof that is sensitive to a first shear force component (i.e., aF_(X) strain gage). The first transducer beam 706 and the fourthtransducer beam 712 also each comprise a plurality of spaced apartstrain gages 728 (e.g., two spaced apart strain gages 728) disposed onan outer side surface thereof that is sensitive to a second shear forcecomponent (i.e., a F_(Y) strain gage).

FIG. 24 illustrates a load transducer 800 according to a tenth exemplaryembodiment of the present invention. With reference to this figure, itcan be seen that, in some respects, the tenth exemplary embodiment issimilar to that of the preceding embodiments. Moreover, some parts arecommon to all of the embodiments. For the sake of brevity, the partsthat the tenth embodiment of the load transducer has in common with thepreceding embodiments will only be briefly mentioned because thesecomponents have already been explained in detail above.

Initially, referring to the perspective view of FIG. 24 , it can be seenthat the load transducer 800 generally includes a one-piece compacttransducer frame 804 with a central body portion 802 and a plurality ofL-shaped transducer beams 806, 808, 810, 812 connected thereto. As shownin FIG. 24 , each of the L-shaped transducer beams 806, 808, 810, 812 isgenerally disposed at a respective corner of the central body portion802.

With reference again to FIG. 24 , it can be seen that the illustratedcentral body portion 802 is generally in the form of square band-shapedelement with a central opening 826 disposed therethrough. In FIG. 24 ,it can be seen that the body portion 802 comprises a first pair ofopposed side portions 802 a, 802 c and a second pair of opposed sideportions 802 b, 802 d. The side portion 802 a is disposed generallyparallel to the side portion 802 c, while the side portion 802 b isdisposed generally parallel to the side portion 802 d. Each of the sidesurfaces of the side portions 802 a, 802 b, 802 c, 802 d is disposedgenerally perpendicular to the planar top and bottom surfaces thereof.Also, each of the first pair of opposed side portions 802 a, 802 c isdisposed generally perpendicular to each of the second pair of opposedsides portions 802 b, 802 d. In addition, as shown in FIG. 24 , each ofthe corners of the central body portion 802 is connected to a respectiveL-shaped transducer beam 806, 808, 810, 812. In the illustratedembodiment, it can be seen that each of the opposed side portions 802 a,802 c comprises a plurality of apertures 828 (e.g., two apertures 828)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 800 to another object, such as a robotic arm,etc. Also, as depicted in the FIG. 24 , the central body portion 802comprises a raised bottom portion or bottom standoff portion 816 forspacing the L-shaped transducer beams 806, 808, 810, 812 apart from anobject (e.g., robotic arm) to which the load transducer 800 is attachedso that forces and/or moments are capable of being accurately measuredby the load transducer 800.

As shown in FIG. 24 , the first generally L-shaped transducer beam 806comprises a first beam portion 806 a and a second beam portion 806 b,wherein the first beam portion 806 a is disposed generally perpendicularto the second beam portion 806 b. Similarly, the second generallyL-shaped transducer beam 808 comprises a first beam portion 808 a and asecond beam portion 808 b, wherein the first beam portion 808 a isdisposed generally perpendicular to the second beam portion 808 b. Also,it can be seen in FIG. 24 that the first beam portion 806 a of the firstgenerally L-shaped transducer beam 806 and the first beam portion 808 aof the second generally L-shaped transducer beam 808 are both generallyaxially aligned with the side portion 802 a of the central body portion802 (i.e., the longitudinal axes of the beam portions 806 a, 808 a aregenerally aligned with the longitudinal axis of the side portion 802 a).With reference again to FIG. 24 , the third generally L-shapedtransducer beam 810 comprises a first beam portion 810 a and a secondbeam portion 810 b, wherein the first beam portion 810 a is disposedgenerally perpendicular to the second beam portion 810 b. Similarly, thefourth generally L-shaped transducer beam 812 comprises a first beamportion 812 a and a second beam portion 812 b, wherein the first beamportion 812 a is disposed generally perpendicular to the second beamportion 812 b. Also, it can be seen in FIG. 24 that the first beamportion 810 a of the third generally L-shaped transducer beam 810 andthe first beam portion 812 a of the fourth generally L-shaped transducerbeam 812 are both generally axially aligned with the side portion 802 cof the central body portion 802 (i.e., the longitudinal axes of the beamportions 810 a, 812 a are generally aligned with the longitudinal axisof the side portion 802 c). Also, in FIG. 24 , it can be seen that thefree ends of the second beam portions 806 b, 808 b, 810 b, 812 b of theL-shaped transducer beams 806, 808, 810, 812 are each provided withraised standoff portions 814. Each raised standoff portion 814 isprovided with a mounting aperture 818 disposed therethrough foraccommodating a respective fastener (e.g., a screw) that attaches theload transducer 800 to another object, such as a robotic arm, etc.

As best shown in the perspective view of FIG. 24 , the illustrated loadcells are located on the L-shaped transducer beams 806, 808, 810, 812.In the illustrated embodiment, each load cell comprises one or morestrain gages 820, 822, 824. Specifically, in the illustrated embodiment,the second beam portions 806 b, 808 b, 810 b, 812 b of the L-shapedtransducer beams 806, 808, 810, 812 are each provided with a strain gage820 disposed on the top surface thereof that is sensitive to thevertical force component (i.e., an F_(Z) strain gage). In FIG. 24 , itcan be seen that each of the strain gages 820 is disposed near theraised standoff portions 818 of the second beam portions 806 b, 808 b,810 b, 812 b. Also, in the illustrated embodiment, the second beamportions 806 b, 808 b, 810 b, 812 b of the L-shaped transducer beams806, 808, 810, 812 each comprise a strain gage 822 disposed on an outerside surface thereof that is sensitive to a first shear force component(i.e., a F_(X) strain gage). The first beam portions 806 a, 808 a, 810a, 812 a of the L-shaped transducer beams 806, 808, 810, 812 eachcomprise a strain gage 824 disposed on an outer side surface thereofthat is sensitive to a second shear force component (i.e., a F_(Y)strain gage).

In the illustrated embodiments of the present invention, the transducerbeams do not extend from a top or upper surface of the central bodyportion. As such, there is no gap formed between the top or uppersurface of the central body portion and a bottom or lower surface of oneor more of the transducer beams. Rather, in the exemplary embodimentscomprising a central body portion, the transducer beams extend outwardlyfrom a side or lateral surface of the central body portion so as tominimize the overall height of the transducer profile (i.e., because thetransducer beams are not required to be disposed above the central bodyportion). Also, in the illustrated embodiments discussed above, thetransducer beams are not in the form of generally linear beams, and arenot in the form of generally linear beams with generally symmetrical endportions. Rather, the transducer beams of the exemplary embodimentsgenerally either emanate from a central body portion and have only onecantilevered end or are arranged in a continuous band-likeconfiguration. In addition, it can be seen that, except for the top andbottom standoff portions on either the transducer beams or the centralbody portions, the top and bottom surfaces of the transducer beams ofthe exemplary embodiments are generally co-planar with the respectivetop and bottom surfaces of the central body portion. Similarly, in theexemplary embodiments having a band-like configuration of transducerbeams, the top surfaces of each of the looped transducer beams aregenerally co-planar with one another, while the bottom surfaces of eachof the looped transducer beams are also generally co-planar with oneanother.

FIGS. 26-29 illustrate a load transducer 900 according to an eleventhexemplary embodiment of the present invention. Referring initially tothe top perspective view of FIG. 26 , it can be seen that the loadtransducer 900 generally includes a one-piece compact transducer frame902 having a plurality of transducer beam portions 904, 906, 908, 910,912 connected to one another in succession. As best shown in theperspective views of FIGS. 26 and 29 , the plurality of transducer beamportions 904, 906, 908, 910, 912 are arranged in a circumscribingpattern whereby a central one of the plurality of transducer beamportions (i.e., transducer beam portion 904) is at least partiallycircumscribed by one or more outer ones of the plurality of beamportions (i.e., transducer beam portions 906, 908, 910, 912). In otherwords, the plurality of transducer beam portions 904, 906, 908, 910, 912forming the load transducer 900 are arranged in a looped configurationwhereby a central one of the plurality of beam portions (i.e.,transducer beam portion 904) emanates from a generally central locationwithin a footprint of the load transducer 900 and outer ones of theplurality of beam portions (i.e., transducer beam portions 906, 908,910, 912) are wrapped around the central one of the plurality of beamportions. As best illustrated in the perspective views of FIGS. 26 and29 , each of the beam portions 908, 910, 912 comprise one or more loadcells or transducer elements for measuring forces and/or moments.

As shown in FIGS. 26-29 , the illustrated transducer beam portions 904,906, 908, 910, 912 are arranged in a generally spiral-shaped patternthat emanates from the centrally located transducer beam portion 904.The pattern in which the transducer beam portions 904, 906, 908, 910,912 are arranged is also generally G-shaped (refer to FIGS. 26 and 29 ).With particular reference to the perspective views of FIGS. 26 and 29 ,it can be seen that the transducer beam portions 904, 906, 908, 910, 912of the load transducer 900 are arranged in such a configuration thateach of the successive transducer beam portions are disposedsubstantially perpendicular to the immediately preceding transducer beamportion. For example, referring to FIG. 26 , the first transducer beamportion 904 is disposed at the approximate center of the transducerfootprint, the second transducer beam portion 906 is connected to thefirst transducer beam portion 904 and is disposed substantiallyperpendicular thereto, the third transducer beam portion 908 isconnected to the second transducer beam portion 906 and is disposedsubstantially perpendicular thereto, the fourth transducer beam portion910 is connected to the third transducer beam portion 908 and isdisposed substantially perpendicular thereto, and the fifth transducerbeam portion 912 is connected to the fourth transducer beam portion 910and is disposed substantially perpendicular thereto. In FIGS. 26 and 29, it can be seen that the transducer beam portions 904, 906, 908, 910,912 of the load transducer 900 are spaced apart from one another by agenerally U-shaped, central gap 942, which is bounded by each of thetransducer beam portions 904, 906, 908, 910, 912. In particular, thefirst transducer beam portion 904 and the third transducer beam portion908, which are disposed generally parallel to one another, are laterallyspaced apart by the gap 942. Similarly, the second transducer beamportion 906 and the fourth transducer beam portion 910, which aredisposed generally parallel to one another, are laterally spaced apartby the gap 942. Also, the first transducer beam portion 904 and thefifth transducer beam portion 912, which are disposed generally parallelto one another, are laterally spaced apart by the gap 942. The thirdtransducer beam portion 908 and the fifth transducer beam portion 912,which are disposed generally parallel to one another, are laterallyspaced apart by the gap 942 and a segment of the first transducer beamportion 904.

Referring again to the top perspective view of FIG. 26 , it can be seenthat the first and second transducer beam portions 904, 906 of the loadtransducer 900 together comprise an L-shaped raised portion or standoffportion 920 with mounting apertures 924 (e.g., three apertures 924)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the load transducer 900 to another object, such as a platecomponent of a force plate or force measurement assembly. The mountingapertures 924 pass completely through the first and second transducerbeam portions 904, 906, and are provided with respective bottom boreportions 924 a of increased diameter (see FIG. 29 ) in order toaccommodate fasteners (e.g., screws) with fillister heads that have alarger outer diameter than the threaded portions of the fasteners. Inaddition, with reference again to FIG. 26 , it can be seen that theelevated L-shaped top surface of the first and second transducer beamportions 904, 906 is provided with pin locating bores 926 (e.g., twobores 926) formed therein for receiving locating pins that ensure theproper positioning of the load transducer 900 on the object to which itis mounted, such as a plate component of a force plate or forcemeasurement assembly. The locating pins are received within the pinlocating bores 926 on the load transducer 900 and within correspondingpin locating bores provided on the object (e.g., the force plate orforce measurement assembly). As depicted in the bottom perspective viewof FIG. 29 , the fifth transducer beam portion 912 of the loadtransducer 900 comprises a generally rectangular or square raisedportion or standoff portion 922 with a mounting aperture 928 (e.g., asingle aperture 928) disposed therethrough for accommodating a fastener(e.g., a screw) that attaches the load transducer 900 to another object,such as a mounting foot of a force plate or force measurement assembly.Advantageously, the standoff portions 920, 922 on the top and bottom ofthe load transducer 900 elevate the transducer beam portions 904, 906,908, 910, 912 above the object(s) to which the load transducer 900 isattached so that forces and/or moments are capable of being accuratelymeasured by the load transducer 900. In one or more embodiments, thestructural components to which the load transducer 900 is mounted areconnected only to the top standoff portion 920 and the bottom standoff922 so as to ensure that the total load applied to the load transducer900 is transmitted through the transducer beam portions 904, 906, 908,910, 912.

In the illustrative embodiment, the third, fourth, and fifth transducerbeam portions 908, 910, 912 have a top surface that is disposed at afirst elevation relative to a bottom surface of the load transducer 900,whereas the L-shaped raised portion 920 of the first and secondtransducer beam portions 904, 906 has a top surface that is disposed ata second elevation relative to the bottom surface of the load transducer900. As best shown in FIGS. 26-28 , the second elevation is greater thanthe first elevation such that a recessed area is created by thedifference in elevation between the second elevation and the firstelevation. In the illustrated embodiment, the recessed area is used toaccommodate electrical components of the transducer load cells (e.g.,strain gages 934, 936 a, 938 a).

In the illustrative embodiment of FIGS. 26-29 , each of the transducerbeam portions 908, 910, 912 is provided with a respective aperture 914,916, 918 disposed therethrough. In particular, the third transducer beamportion 908 is provided with a generally rectangular aperture 914disposed vertically through the beam portion. Similarly, the fourthtransducer beam portion 910 is provided with a generally rectangularaperture 916 disposed vertically through the beam portion. The fifthtransducer beam portion 912 is provided with a generally rectangularaperture 918 disposed horizontally through the beam portion. Theapertures 914, 916, 918, which are disposed through the respectivetransducer beam portions 908, 910, 912, significantly increase thesensitivity of the load transducer 900 when a load is applied thereto byreducing the cross-sectional area of the transducer beam portions 908,910, 912 at the locations of the apertures 914, 916, 918.

As best shown in the perspective views of FIGS. 26 and 29 , theillustrated load cells are located on the transducer beam portions 908,910, 912. In the illustrated embodiment, each load cell comprises one ormore strain gages 930, 932, 934, 936 a, 936 b, 938 a, 938 b, 940 a, and940 b. Specifically, in the illustrated embodiment, the third transducerbeam portion 908 of the load transducer 900 comprises a strain gage 932disposed on a side surface thereof that is sensitive to a first shearforce component (i.e., a F_(Y) strain gage) and substantially centeredon the aperture 914. The third transducer beam portion 908 alsocomprises a set of strain gages 938 a, 938 b that are sensitive to afirst moment component (i.e., a M_(Y) strain gages). The strain gages938 a, 938 b are disposed on opposed side surfaces (e.g., top and bottomsurfaces) of the third transducer beam portion 908, and aresubstantially vertically aligned with one another. Turning again toFIGS. 26 and 29 , in the illustrated embodiment, the fourth transducerbeam portion 910 of the load transducer 900 comprises a strain gage 930disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 916. The fourth transducer beam portion 910 alsocomprises a set of strain gages 936 a, 936 b that are sensitive to asecond moment component (i.e., a M_(X) strain gages). Like the straingages 938 a, 938 b, the strain gages 936 a, 936 b are disposed onopposed side surfaces (e.g., top and bottom surfaces) of the fourthtransducer beam portion 910, and are substantially vertically alignedwith one another. With reference again to FIGS. 26 and 29 , in theillustrated embodiment, the fifth transducer beam portion 912 of theload transducer 900 comprises a strain gage 934 disposed on the topsurface thereof that is sensitive to a vertical force component (i.e., aF_(Z) strain gage) and substantially centered on the aperture 918. Thefifth transducer beam portion 912 also comprises a set of strain gages940 a, 940 b that are sensitive to a third moment component (i.e., aM_(Z) strain gages). Like the strain gages 936 a, 936 b and 938 a, 938b, the strain gages 940 a, 940 b are disposed on opposed side surfaces(e.g., first and second lateral surfaces) of the fifth transducer beamportion 912, and are substantially horizontally aligned with oneanother. In the illustrated embodiment, the first shear force componentis generally perpendicular to the second shear force component, and eachof the first and second shear force components are generallyperpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 930, 932, 934 aredisposed on respective outer surfaces of the transducer beam portions910, 908, 912. The outer surfaces of the transducer beam portions 910,908, 912 on which the strain gages 930, 932, 934 are disposed aregenerally opposite to the inner surfaces of the respective apertures916, 914, 918.

As best shown in FIGS. 26 and 29 , the illustrated load cells aremounted on top, bottom, or side surfaces of the transducer beam portions908, 910, 912 between the standoff portions 920, 922 of the loadtransducer 900. Alternatively, the strain gages 932, 930 can be mountedto the inner side surfaces of the respective third and fourth transducerbeam portions 908, 910, rather than to the outer side surfaces of therespective third and fourth transducer beam portions 908, 910 asillustrated in FIGS. 26 and 29 . Similarly, the strain gage 934 can bemounted to the bottom surface of the fifth transducer beam portion 912,rather than to the top of the transducer beam portion 912 as illustratedin FIG. 26 . In general, the strain gages 930, 932, 934 are mounted tosurfaces generally normal to the direction of applied vertical and/orshear forces (i.e., F_(X), F_(Y), F_(Z)). It is also noted thatalternatively, strain gages 930 can be mounted at both opposed sidesurfaces of fourth transducer beam portion 910 and/or strain gages 932can be mounted at both opposed side surfaces of the third transducerbeam portion 908. Similarly, strain gages 934 can be mounted at both thetop surface and the bottom surface of the fifth transducer beam portion912. These strain gages 930, 932, 934 measure force either by bendingmoment or difference of bending moments at two cross sections. As forceis applied to the ends of the load transducer 900, the transducer beamportions bend. This bending either stretches or compresses the straingages 930, 932, 934, which in turn changes the resistance of theelectrical current passing therethrough. The amount of change in theelectrical voltage or current is proportional to the magnitude of theapplied force, as applied to the L-shaped standoff portion 920.

In the illustrated embodiment, each of the strain gages 930, 932, 934comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration), whileeach of the strain gages 936 a, 936 b, 938 a, 938 b, 940 a, and 940 bcomprises a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements). Also, in the illustrative embodiment, the pair ofstrain gages 936 a, 936 b are wired together in one Wheatstone bridgeconfiguration (i.e., with a total of four (4) active strain gageelements), the pair of strain gages 938 a, 938 b are wired together inanother Wheatstone bridge configuration (i.e., with a total of four (4)active strain gage elements), and the pair of strain gages 940 a, 940 bare wired together in yet another Wheatstone bridge configuration (i.e.,with a total of four (4) active strain gage elements).

FIGS. 30-33 illustrate a load transducer 1000 according to a twelfthexemplary embodiment of the present invention. With reference to thesefigures, it can be seen that the load transducer 1000 is similar in manyrespects to the load transducer 900 of the eleventh embodiment describedabove. However, unlike the aforedescribed load transducer 900, the loadtransducer 1000 only measures the force components of a load (i.e.,F_(X), F_(Y), F_(Z)), rather than both the force and moment componentsof a load as explained above with regard to the load transducer 1000.

Initially, referring to the top perspective view of FIG. 30 , it can beseen that the load transducer 1000 generally includes a one-piececompact transducer frame 1002 having a plurality of transducer beamportions 1004, 1006, 1008, 1010, 1012 connected to one another insuccession. As best shown in the perspective views of FIGS. 30 and 33 ,the plurality of transducer beam portions 1004, 1006, 1008, 1010, 1012are arranged in a circumscribing pattern whereby a central one of theplurality of transducer beam portions (i.e., transducer beam portion1004) is at least partially circumscribed by one or more outer ones ofthe plurality of beam portions (i.e., transducer beam portions 1006,1008, 1010, 1012). In other words, the plurality of transducer beamportions 1004, 1006, 1008, 1010, 1012 forming the load transducer 1000are arranged in a looped configuration whereby a central one of theplurality of beam portions (i.e., transducer beam portion 1004) emanatesfrom a generally central location within a footprint of the loadtransducer 1000 and outer ones of the plurality of beam portions (i.e.,transducer beam portions 1006, 1008, 1010, 1012) are wrapped around thecentral one of the plurality of beam portions. As best illustrated inthe perspective views of FIGS. 30 and 33 , each of the beam portions1008, 1010, 1012 comprise one or more load cells or transducer elementsfor measuring the various components of an applied force.

As shown in FIGS. 30-33 , the illustrated transducer beam portions 1004,1006, 1008, 1010, 1012 are arranged in a generally spiral-shaped patternthat emanates from the centrally located transducer beam portion 1004.The pattern in which the transducer beam portions 1004, 1006, 1008,1010, 1012 are arranged is also generally G-shaped (refer to FIGS. 30and 33 ). With particular reference to the perspective views of FIGS. 30and 33 , it can be seen that the transducer beam portions 1004, 1006,1008, 1010, 1012 of the load transducer 1000 are arranged in such aconfiguration that each of the successive transducer beam portions aredisposed substantially perpendicular to the immediately precedingtransducer beam portion. For example, referring to FIG. 30 , the firsttransducer beam portion 1004 is disposed at the approximate center ofthe transducer footprint, the second transducer beam portion 1006 isconnected to the first transducer beam portion 1004 and is disposedsubstantially perpendicular thereto, the third transducer beam portion1008 is connected to the second transducer beam portion 1006 and isdisposed substantially perpendicular thereto, the fourth transducer beamportion 1010 is connected to the third transducer beam portion 1008 andis disposed substantially perpendicular thereto, and the fifthtransducer beam portion 1012 is connected to the fourth transducer beamportion 1010 and is disposed substantially perpendicular thereto. InFIGS. 30 and 33 , it can be seen that the transducer beam portions 1004,1006, 1008, 1010, 1012 of the load transducer 1000 are spaced apart fromone another by a generally U-shaped, central gap 1032, which is boundedby each of the transducer beam portions 1004, 1006, 1008, 1010, 1012. Inparticular, the first transducer beam portion 1004 and the thirdtransducer beam portion 1008, which are disposed generally parallel toone another, are laterally spaced apart by the gap 1032. Similarly, thesecond transducer beam portion 1006 and the fourth transducer beamportion 1010, which are disposed generally parallel to one another, arelaterally spaced apart by the gap 1032. Also, the first transducer beamportion 1004 and the fifth transducer beam portion 1012, which aredisposed generally parallel to one another, are laterally spaced apartby the gap 1032. The third transducer beam portion 1008 and the fifthtransducer beam portion 1012, which are disposed generally parallel toone another, are laterally spaced apart by the gap 1032 and a segment ofthe first transducer beam portion 1004.

Referring again to the top perspective view of FIG. 30 , it can be seenthat the first and second transducer beam portions 1004, 1006 of theload transducer 1000 comprise an L-shaped arrangement of mountingapertures 1020 (e.g., three (3) apertures 1020) disposed therethroughfor accommodating fasteners (e.g., screws) that attach the loadtransducer 1000 to another object, such as a plate component of a forceplate or force measurement assembly. The mounting apertures 1020 passcompletely through the first and second transducer beam portions 1004,1006, and are provided with respective bottom bore portions 1020 a ofincreased diameter (see FIG. 33 ) in order to accommodate fasteners(e.g., screws) with fillister heads that have a larger outer diameterthan the threaded portions of the fasteners. In addition, with referenceagain to FIG. 30 , it can be seen that the L-shaped portion of the loadtransducer 1000 that is formed by the first and second transducer beamportions 1004, 1006 is provided with pin locating bores 1022 (e.g., two(2) bores 1022) formed therein for receiving locating pins that ensurethe proper positioning of the load transducer 1000 on the object towhich it is mounted, such as a plate component of a force plate or forcemeasurement assembly. The locating pins are received within the pinlocating bores 1022 on the load transducer 1000 and within correspondingpin locating apertures provided on the object (e.g., the force plate orforce measurement assembly). As depicted in the perspective views ofFIGS. 30 and 33 , the fifth transducer beam portion 1012 of the loadtransducer 1000 comprises a mounting aperture 1024 (e.g., a singleaperture 1024 proximate to the free end thereof) disposed therethroughfor accommodating a fastener (e.g., a screw) that attaches the loadtransducer 1000 to another object, such as a mounting foot of a forceplate or force measurement assembly. In one or more embodiments, theload transducer 1000 is connected to one or more objects in such amanner that the total load applied to the load transducer 1000 istransmitted through the transducer beam portions 1004, 1006, 1008, 1010,1012.

In the illustrative embodiment of FIGS. 30-33 , each of the transducerbeam portions 1008, 1010, 1012 is provided with a respective aperture1014, 1016, 1018 disposed therethrough. In particular, the thirdtransducer beam portion 1008 is provided with a generally rectangularaperture 1014 disposed vertically through the beam portion. Similarly,the fourth transducer beam portion 1010 is provided with a generallyrectangular aperture 1016 disposed vertically through the beam portion.The fifth transducer beam portion 1012 is provided with a generallyrectangular aperture 1018 disposed horizontally through the beamportion. The apertures 1014, 1016, 1018, which are disposed through therespective transducer beam portions 1008, 1010, 1012, significantlyincrease the sensitivity of the load transducer 1000 when a load isapplied thereto by reducing the cross-sectional area of the transducerbeam portions 1008, 1010, 1012 at the locations of the apertures 1014,1016, 1018.

As best shown in the perspective views of FIGS. 30 and 33 , theillustrated load cells are located on the transducer beam portions 1008,1010, 1012. In the illustrated embodiment, each load cell comprises oneor more strain gages 1026, 1028, and 1030. Specifically, in theillustrated embodiment, the third transducer beam portion 1008 of theload transducer 1000 comprises a strain gage 1028 disposed on a sidesurface thereof that is sensitive to a first shear force component(i.e., a F_(Y) strain gage) and substantially centered on the aperture1014. Turning again to FIGS. 30 and 33 , in the illustrated embodiment,the fourth transducer beam portion 1010 of the load transducer 1000comprises a strain gage 1026 disposed on a side surface thereof that issensitive to a second shear force component (i.e., a F_(X) strain gage)and substantially centered on the aperture 1016. With reference again toFIGS. 30 and 33 , in the illustrated embodiment, the fifth transducerbeam portion 1012 of the load transducer 1000 comprises a strain gage1030 disposed on the top surface thereof that is sensitive to a verticalforce component (i.e., a F_(Z) strain gage) and substantially centeredon the aperture 1018. In the illustrated embodiment, the first shearforce component is generally perpendicular to the second shear forcecomponent, and each of the first and second shear force components aregenerally perpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1026, 1028, 1030 aredisposed on respective outer surfaces of the transducer beam portions1010, 1008, 1012. The outer surfaces of the transducer beam portions1010, 1008, 1012 on which the strain gages 1026, 1028, 1030 are disposedare generally opposite to the inner surfaces of the respective apertures1016, 1014, 1018.

As best shown in FIGS. 30 and 33 , the illustrated load cells aremounted on top or side surfaces of the transducer beam portions 1008,1010, 1012 between the ends of the load transducer 1000. Alternatively,the strain gages 1028, 1026 can be mounted to the inner side surfaces ofthe respective third and fourth transducer beam portions 1008, 1010,rather than to the outer side surfaces of the respective third andfourth transducer beam portions 1008, 1010 as illustrated in FIGS. 30and 33 . Similarly, the strain gage 1030 can be mounted to the bottomsurface of the fifth transducer beam portion 1012, rather than to thetop of the transducer beam portion 1012 as illustrated in FIG. 30 . Ingeneral, the strain gages 1026, 1028, 1030 are mounted to surfacesgenerally normal to the direction of applied vertical and/or shearforces (i.e., F_(X), F_(Y), F_(Z)). It is also noted that alternatively,strain gages 1026 can be mounted at both opposed side surfaces of fourthtransducer beam portion 1010 and/or strain gages 1028 can be mounted atboth opposed side surfaces of the third transducer beam portion 1008.Similarly, strain gages 1030 can be mounted at both the top surface andthe bottom surface of the fifth transducer beam portion 1012. Thesestrain gages 1026, 1028, 1030 measure force either by bending moment ordifference of bending moments at two cross sections. As force is appliedto the ends of the load transducer 1000, the transducer beam portionsbend. This bending either stretches or compresses the strain gages 1026,1028, 1030, which in turn changes the resistance of the electricalcurrent passing therethrough. The amount of change in the electricalvoltage or current is proportional to the magnitude of the appliedforce, as applied to the load transducer 1000.

In the illustrated embodiment, each of the strain gages 1026, 1028, 1030comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration) formeasuring the applied vertical and shear forces.

An exemplary embodiment of a force measurement system is illustrated inFIGS. 34-37 . In the illustrative embodiment, the force measurementsystem generally comprises a force measurement assembly 1040 (i.e., aforce plate) that is operatively coupled to a data acquisition/dataprocessing device 1060 (i.e., a data acquisition and processing deviceor computing device that is capable of collecting, storing, andprocessing data). The force measurement assembly 1040 illustrated inFIGS. 34-36 is configured to receive a subject thereon, and is capableof measuring the forces and/or moments applied to its measurementsurface by the subject.

As shown in FIG. 34 , the data acquisition and processing device 1060(e.g., in the form of a laptop digital computer) generally includes abase portion 1064 with a central processing unit (CPU) disposed thereinfor collecting and processing the data that is received from the forcemeasurement assembly 1040, and a plurality of devices 1066-1070operatively coupled to the central processing unit (CPU) in the baseportion 1064. Preferably, the devices that are operatively coupled tothe central processing unit (CPU) comprise user input devices 1066, 1068in the form of a keyboard 1066 and a touchpad 1068, as well as agraphical user interface in the form of a laptop LCD screen 1070. Whilea laptop type computing system is depicted in the embodiment of FIG. 34, one of ordinary skill in the art will appreciate that another type ofdata acquisition and processing device 1060 can be substituted for thelaptop computing system such as, but not limited to, a palmtop computingdevice (i.e., a PDA) or a desktop type computing system having aplurality of separate, operatively coupled components (e.g., a desktoptype computing system including a main housing with a central processingunit (CPU) and data storage devices, a remote monitor, a remotekeyboard, and a remote mouse).

As illustrated in FIG. 34 , force measurement assembly 1040 isoperatively coupled to the data acquisition/data processing device 1060by virtue of an electrical cable 1062. In one embodiment of theinvention, the electrical cable 1062 is used for data transmission, aswell as for providing power to the force measurement assembly 1040.Various types of data transmission cables can be used for cable 1062.For example, the cable 1062 can be a Universal Serial Bus (USB) cable oran Ethernet cable. Preferably, the electrical cable 1062 contains aplurality of electrical wires bundled together, with at least one wirebeing used for power and at least another wire being used fortransmitting data. The bundling of the power and data transmission wiresinto a single electrical cable 1062 advantageously creates a simpler andmore efficient design. In addition, it enhances the safety of thetesting environment when human subjects are being tested on the forcemeasurement assembly 1040. However, it is to be understood that theforce measurement assembly 1040 can be operatively coupled to the dataacquisition/data processing device 1040 using other signal transmissionmeans, such as a wireless data transmission system. If a wireless datatransmission system is employed, it is preferable to provide the forcemeasurement assembly 1040 with a separate power supply in the form of aninternal power supply or a dedicated external power supply.

Referring again to FIG. 34 , it can be seen that the force measurementassembly 1040 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1042 supported on a pluralityof load transducers 1000, 1000′. As shown in FIGS. 34 and 35 , the platecomponent 1042 comprises a top measurement surface 1044, a bottomsurface 1054 disposed generally opposite to the top measurement surface1044, and a plurality of side surfaces 1046, 1048, 1050, 1052 disposedbetween the top and bottom surfaces 1044, 1054. In the illustratedembodiment, the first side surface 1046 of the plate component 1042 isdisposed generally parallel to the second side surface 1048, and isdisposed generally perpendicular to both the third side surface 1050 andthe fourth side surface 1052. The third side surface 1050 of the platecomponent 1042 is disposed generally parallel to the fourth side surface1052, and is disposed generally perpendicular to both the first sidesurface 1046 and the second side surface 1048. Turning to the explodedview of FIG. 36 , it can be seen that the bottom surface 1054 of theplate component 1042 comprises a plurality of transducer mountingrecesses 1056 for accommodating respective ones of the load transducers1000, 1000′. Also, as shown in FIG. 36 , it can be seen that an L-shapedtransducer standoff plate 1034 is provided in each of the transducermounting recesses 1056 for spacing the top surfaces of the loadtransducers 1000, 1000′ from the mounting surfaces of the recesses 1056.Referring again to the bottom perspective view of FIG. 36 , it can beseen that each L-shaped transducer standoff plate 1034 comprises aplurality of mounting apertures 1036 (e.g., three (3) apertures 1036)disposed therethrough for accommodating fasteners (e.g., screws) thatattach the plate component 1042 of the force measurement assembly 1040to either the load transducer 1000 or the load transducer 1000′. Assuch, the mounting apertures 1036 in each L-shaped transducer standoffplate 1034 are substantially aligned with the mounting apertures 1020 inthe load transducers 1000, 1000′ such that they correspond thereto. Inaddition, with reference again to FIG. 36 , it can be seen that eachL-shaped transducer standoff plate 1034 further comprises pin locatingapertures 1038 (e.g., two (2) apertures 1038) formed therein forreceiving locating pins that ensure the proper positioning of the loadtransducers 1000, 1000′ on the plate component 1042 of the forcemeasurement assembly 1040. Thus, the pin locating apertures 1038 in eachL-shaped transducer standoff plate 1034 are substantially aligned withthe pin locating bores 1022 in the load transducers 1000, 1000′ suchthat they correspond thereto. The pin locating apertures 1038 in theL-shaped transducer standoff plates 1034, and the pin locating bores1022 in the load transducers 1000, 1000′, collectively receive locatingpins that ensure the proper positioning of the load transducers 1000,1000′ on the plate component 1042 of the force measurement assembly1040.

In illustrated embodiment of FIGS. 34-36 , the force measurementassembly 1040 comprises a total of four (4) load transducers 1000, 1000′that are disposed underneath, and near each of the respective fourcorners (4) of the plate component 1042. The load transducers 1000′ aregenerally the same as the load transducers 1000, expect that they areconfigured as a mirror image of the load transducers 1000.Advantageously, because the load transducers 1000, 1000′ are compact,none of the plurality of load transducers 1000, 1000′ extendsubstantially an entire length or width of the plate component 1042 ofthe force measurement assembly 1040. The compact construction of theload transducers 1000, 1000′ not only reduces material costs becauseless material is used to form the load transducers 1000, 1000′, but italso allows the load transducers 1000, 1000′ to be universally used onforce plates having a myriad of different lengths and widths because itis not necessary for the load transducers 1000, 1000′ to conform to thefootprint size of the force plate.

In an alternative embodiment, rather than using the load transducers1000, 1000′ on the force measurement assembly 1040, the load transducers900 described above could be provided on the force measurement assembly1040. Using the load transducers 900 in lieu of the load transducers1000, 1000′ would enable the moment components of the load applied tothe plate component 1042 to be measured in addition to the forcecomponents of the load.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1040 having a plate component 1042 with a singlemeasurement surface 1044, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1040illustrated in FIGS. 34-36 , the dual force plate comprises two separateplate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on four (4) load transducers 1000, 1000′ (i.e., a loadtransducer 1000, 1000′ is disposed in each of the respective four (4)corners of each of the two plate components). As such, the dual forceplate comprises a total of eight (8) load transducers 1000, 1000′ (i.e.,four (4) load transducers 1000, 1000′ under each of the two platecomponents).

Also, as shown in FIGS. 34-36 , the force measurement assembly 1040 isprovided with a plurality of support feet 1058 disposed thereunder.Preferably, each of the four (4) corners of the force measurementassembly 1040 is provided with a support foot 1058 (e.g., mounted on thebottom of each load transducer 1000, 1000′). In particular, in theillustrated embodiment, each support foot 1058 is attached to anaperture 1024 in a respective one of the load transducers 1000, 1000′ bymeans of a fastener (e.g., a screw). In one embodiment, at least one ofthe support feet 1058 is adjustable so as to facilitate the leveling ofthe force measurement assembly 1040 on an uneven floor surface.

Now, turning to FIG. 37 , it can be seen that the data acquisition/dataprocessing device 1060 (i.e., the laptop computing device) of the forcemeasurement system comprises a microprocessor 1060 a for processingdata, memory 1060 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1060 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 37 , theforce measurement assembly 1040 and the visual display device 1070 areoperatively coupled to the core components 1060 a, 1060 b, 1060 c of thedata acquisition/data processing device 1060 such that data is capableof being transferred between these devices 1040, 1060 a, 1060 b, 1060 c,and 1070. Also, as illustrated in FIG. 37 , a plurality of data inputdevices 1066, 1068 such as the keyboard 1066 and mouse 1068 shown inFIG. 34 , are operatively coupled to the core components 1060 a, 1060 b,1060 c of the data acquisition/data processing device 1060 so that auser is able to enter data into the data acquisition/data processingdevice 1060. In some embodiments, the data acquisition/data processingdevice 1060 can be in the form of a laptop computer, while in otherembodiments, the data acquisition/data processing device 1060 can beembodied as a desktop computer.

FIG. 38 graphically illustrates the acquisition and processing of theload data carried out by the exemplary force measurement system of FIG.34 . Initially, as shown in FIG. 38 , a load L is applied to the forcemeasurement assembly 1040 (e.g., by a subject disposed thereon). Theload is transmitted from the plate component 1042 to the loadtransducers 1000, 1000′ disposed in each of its four (4) corners. Asdescribed above, in the illustrated embodiment, each of the loadtransducers 1000, 1000′ includes a plurality of strain gages 1026, 1028,1030 wired in one or more Wheatstone bridge configurations, wherein theelectrical resistance of each strain gage is altered when the associatedbeam portion of the load transducer 1000, 1000′ undergoes deformationresulting from the load (i.e., forces and/or moments) acting on theplate component 1042. For each plurality of strain gages disposed on theload transducers 1000, 1000′, the change in the electrical resistance ofthe strain gages brings about a consequential change in the outputvoltage of the Wheatstone bridge (i.e., a quantity representative of theload being applied to the measurement surface 1044). Thus, in oneembodiment, the four (4) load transducers 1000, 1000′ disposed under theplate component 1042 output a total of twelve (12) analog outputvoltages (signals). In some embodiments, the twelve (12) analog outputvoltages from load transducers 1000, 1000′ disposed under the platecomponent 1042 are then transmitted to a preamplifier board (not shown)for preconditioning. The preamplifier board is used to increase themagnitudes of the transducer analog voltages, and preferably, to convertthe analog voltage signals into digital voltage signals as well. Afterwhich, the force measurement assembly 1040 transmits the force plateoutput signals S_(FPO1)-S_(FP12) to a main signal amplifier/converter1072. Depending on whether the preamplifier board also includes ananalog-to-digital (A/D) converter, the force plate output signalsS_(FPO1)-S_(FP12) could be either in the form of analog signals ordigital signals. The main signal amplifier/converter 1072 furthermagnifies the force plate output signals S_(FPO1)-S_(FP12), and if thesignals S_(FPO1)-S_(FP12) are of the analog-type (for a case where thepreamplifier board did not include an analog-to-digital (A/D)converter), it may also convert the analog signals to digital signals.Then, the signal amplifier/converter 1072 transmits either the digitalor analog signals S_(ACO1)-S_(AC12) to the data acquisition/dataprocessing device 1060 (computer 1060) so that the forces and/or momentsthat are being applied to the measurement surface 1044 of the forcemeasurement assembly 1040 can be transformed into output load values OL.In addition to the components 1060 a, 1060 b, 1060 c, the dataacquisition/data processing device 1060 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(AC12) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor 1060 a.

When the data acquisition/data processing device 1060 receives thevoltage signals S_(ACO1)-S_(AC12), it initially transforms the signalsinto output forces by multiplying the voltage signals S_(ACO1)-S_(AC12)by a calibration matrix. If the load transducer 900 is used inconjunction with the force measurement assembly 1040, the dataacquisition/data processing device 1060 may additionally transform thesignals into output moments by multiplying the voltage signals by thecalibration matrix. After which, the force exerted on the surface 1044of the force measurement assembly 1040, and the center of pressure ofthe applied force (i.e., the x and y coordinates of the point ofapplication of the force applied to the measurement surface 1044) isdetermined by the data acquisition/data processing device 1060.Referring to the perspective view of FIG. 34 , it can be seen that thecenter of pressure coordinates (x_(P) _(L) , y_(P) _(L) ) for the platecomponent 1042 of the force measurement assembly 1040 are determined inaccordance with x and y coordinate axes 1074, 1076.

In one exemplary embodiment, the data acquisition/data processing device1060 determines all three (3) orthogonal components of the resultantforces acting on the plate component 1042 of the force measurementassembly 1040 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments ofthe invention, all three (3) orthogonal components of the resultantforces and moments acting on the plate component 1042 of the forcemeasurement assembly 1040 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y),M_(Z)) may be determined (i.e., when the load transducer 900 is used inlieu of the load transducers 1000, 1000′).

FIGS. 39-41 illustrate a load transducer 1100 according to a thirteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 39 , it can be seen that the loadtransducer 1100 generally includes a one-piece compact transducer frame1104 having a central body portion 1102 and a plurality of beam portions1106, 1108, 1110, 1112 extending along sides 1102 a, 1102 b, 1102 c ofthe central body portion 1102. As best illustrated in the perspectiveview of FIG. 39 , each of the beam portions 1106, 1108, 1110, 1112comprises one or more load cells or transducer elements for measuringforces and/or moments.

With reference again to FIG. 39 , it can be seen that the illustratedcentral body portion 1102 is generally in the form of a square prismwith substantially right angle corners (i.e., substantially 90 degreecorners). In FIG. 39 , it can be seen that the body portion 1102comprises a first pair of opposed sides 1102 a, 1102 c and a second pairof opposed sides 1102 b, 1102 d. The side 1102 a is disposed generallyparallel to the side 1102 c, while the side 1102 b is disposed generallyparallel to the side 1102 d. Each of the sides 1102 a, 1102 b, 1102 c,1102 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1102. Also, each of the first pair ofopposed sides 1102 a, 1102 c is disposed generally perpendicular to eachof the second pair of opposed sides 1102 b, 1102 d. In addition, asshown in FIG. 39 , the second side 1102 b comprises a beam connectingportion 1114 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1114 connects the beamportions 1106 and 1110 to the second side 1102 b of the central bodyportion 1102. In the illustrated embodiment, the total load applied tothe load transducer 1100 is transmitted through the beam portions 1106,1108, 1110, 1112.

As best shown in FIGS. 39 and 41 , the proximal end of the first beamportion 1106 is rigidly connected to the central body portion 1102 bymeans of the beam connecting portion 1114, and the distal end of thefirst beam portion 1106 is rigidly connected to the proximal end of thesecond beam portion 1108. As depicted in these figures, the first beamportion 1106 extends along the second side 1102 b of the central bodyportion 1102, and the second beam portion 1108 extends along the firstside 1102 a of the central body portion 1102. More particularly, in theillustrative embodiment, the longitudinal axis of the first beam portion1106 is disposed generally parallel to the second side 1102 b of thecentral body portion 1102, and the longitudinal axis of the second beamportion 1108 is disposed generally parallel to the first side 1102 a ofthe central body portion 1102. As best shown in the perspective view ofFIG. 39 , the top and bottom surfaces of each of the first and secondbeam portions 1106, 1108 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1102. Also, in theillustrative embodiment, with reference again to FIGS. 39 and 41 , thefirst beam portion 1106 is generally perpendicular, or perpendicular tothe second beam portion 1108 (i.e., together the first and second beamportions 1106, 1108 form an overall L-shaped beam arm). In addition, asshown in these figures, the first beam portion 1106 is spaced apart fromthe second side 1102 b of the central body portion 1102 by a first gap1128, and the second beam portion 1108 is spaced apart from the firstside 1102 a of the central body portion 1102 by a second gap 1130. Inthe illustrative embodiment, together the first gap 1128 and the secondgap 1130 form an overall L-shaped gap (i.e., the first gap 1128 isdisposed perpendicular to the second gap 1130).

Also, referring again to FIGS. 39 and 41 , it can be seen that theproximal end of the third beam portion 1110 is rigidly connected to thecentral body portion 1102 by means of the beam connecting portion 1114,and the distal end of the third beam portion 1110 is rigidly connectedto the proximal end of the fourth beam portion 1112. As depicted inthese figures, the third beam portion 1110 extends along the second side1102 b of the central body portion 1102, and the fourth beam portion1112 extends along the third side 1102 c of the central body portion1102. More particularly, in the illustrative embodiment, thelongitudinal axis of the third beam portion 1110 is disposed generallyparallel to the second side 1102 b of the central body portion 1102, andthe longitudinal axis of the fourth beam portion 1112 is disposedgenerally parallel to the third side 1102 c of the central body portion1102. As best shown in the perspective view of FIG. 39 , the top andbottom surfaces of each of the third and fourth beam portions 1110, 1112are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1102. Also, in the illustrative embodiment,with reference again to FIGS. 39 and 41 , the third beam portion 1110 isgenerally perpendicular, or perpendicular to the fourth beam portion1112 (i.e., together the third and fourth beam portions 1110, 1112 forman overall L-shaped beam arm). In addition, as shown in these figures,the third beam portion 1110 is spaced apart from the second side 1102 bof the central body portion 1102 by a third gap 1132, and the fourthbeam portion 1112 is spaced apart from the third side 1102 c of thecentral body portion 1102 by a fourth gap 1134. In the illustrativeembodiment, together the third gap 1132 and the fourth gap 1134 form anoverall L-shaped gap (i.e., the third gap 1132 is disposed perpendicularto the fourth gap 1134).

In the illustrative embodiment of FIGS. 39 and 41 , it can be seen thatthe free end 1108 a of the second beam portion 1108 is generallyaligned, or aligned with the fourth side 1102 d of the central bodyportion 1102 (i.e., the end face of the second beam portion 1108 isco-planar with the fourth side 1102 d of the central body portion 1102).Also, as shown in FIGS. 39 and 41 , the free end 1112 a of the fourthbeam portion 1112 is generally aligned, or aligned with the fourth side1102 d of the central body portion 1102 (i.e., the end face of thefourth beam portion 1112 is co-planar with the fourth side 1102 d of thecentral body portion 1102).

In the illustrative embodiment of FIGS. 39-41 , the first beam portion1106 is provided with an aperture 1116 disposed therethrough, the secondbeam portion 1108 is provided with apertures 1118, 1120 disposedtherethrough, the third beam portion 1110 is provided with an aperture1122 disposed therethrough, and the fourth beam portion 1112 is providedwith apertures 1124, 1126 disposed therethrough. In particular, thefirst and third transducer beam portions 1106, 1110 are provided withrespective generally rectangular apertures 1116, 1122 disposedvertically through the beam portions 1106, 1110. The second transducerbeam portion 1108 is provided with a first generally rectangularaperture 1118 disposed vertically through the beam portion 1108 and asecond generally rectangular aperture 1120 disposed horizontally throughthe beam portion 1108. As such, the vertically extending aperture 1118of the second beam portion 1108 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1120. Similarly, the fourth transducerbeam portion 1112 is provided with a first generally rectangularaperture 1124 disposed vertically through the beam portion 1112 and asecond generally rectangular aperture 1126 disposed horizontally throughthe beam portion 1112. As such, the vertically extending aperture 1124of the fourth beam portion 1112 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1126. The apertures 1116, 1118, 1120,1122, 1124, 1126, which are disposed through the transducer beamportions 1106, 1108, 1110, 1112, significantly increase the sensitivityof the load transducer 1100 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1106, 1108,1110, 1112 at the locations of the apertures 1116, 1118, 1120, 1122,1124, 1126.

As best shown in the perspective view of FIG. 39 , the illustrated loadcells are located on the transducer beam portions 1106, 1108, 1110,1112. In the illustrated embodiment, each load cell comprises one ormore strain gages 1136, 1138, 1140. Specifically, in the illustratedembodiment, the first transducer beam portion 1106 of the loadtransducer 1100 comprises a strain gage 1136 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(Y) strain gage) and substantially centered on the aperture 1116. Inthe illustrated embodiment, the second transducer beam portion 1108 ofthe load transducer 1100 comprises a strain gage 1138 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(X) strain gage) and substantially centered on the aperture1118. The second transducer beam portion 1108 also comprises a straingage 1140 disposed on a top surface thereof that is sensitive to avertical force component (i.e., a F_(Z) strain gage) and substantiallycentered on the aperture 1120. Also, in the illustrative embodiment, thethird transducer beam portion 1110 of the load transducer 1100 comprisesa strain gage 1136 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1122. The fourth transducer beamportion 1112 of the load transducer 1100 comprises a strain gage 1138disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 1124. The fourth transducer beam portion 1112 alsocomprises a strain gage 1140 disposed on a top surface thereof that issensitive to a vertical force component (i.e., a F_(Z) strain gage) andsubstantially centered on the aperture 1126. In the illustratedembodiment, the first shear force component is generally perpendicularto the second shear force component, and each of the first and secondshear force components are generally perpendicular to the vertical forcecomponent.

In the illustrated embodiment, the strain gages 1136, 1138, 1140 aredisposed on respective outer surfaces of the transducer beam portions1106, 1108, 1110, 1112. The outer surfaces of the transducer beamportions 1106, 1108, 1110, 1112 on which the strain gages 1136, 1138,1140 are disposed are generally opposite to the inner surfaces of therespective apertures 1116, 1118, 1120, 1122, 1124, 1126.

As best shown in FIGS. 39-41 , the illustrated load cells are mounted onthe top and outer side surfaces of the transducer beam portions 1106,1108, 1110, 1112 of the load transducer 1100. Alternatively, the straingages 1136, 1138 can be mounted to the inner side surfaces of therespective first and second transducer beam portions 1106, 1108, ratherthan to the outer side surfaces of the respective first and secondtransducer beam portions 1106, 1108 as illustrated in FIGS. 39 and 40 .Similarly, the strain gages 1136, 1138 can be mounted to the inner sidesurfaces of the respective third and fourth transducer beam portions1110, 1112, rather than to the outer side surfaces of the respectivethird and fourth transducer beam portions 1110, 1112 as illustrated inFIGS. 39 and 41 . In addition, the strain gages 1140 can be mounted tothe bottom surfaces of the second and fourth transducer beam portions1108, 1112, rather than to the top of the transducer beam portions 1108,1112 as illustrated in FIGS. 39 and 41 . In general, the strain gages1136, 1138, 1140 are mounted to surfaces generally normal to thedirection of applied vertical and/or shear forces (i.e., F_(X), F_(Y),F_(Z)). It is also noted that alternatively, strain gages 1136 can bemounted at both opposed side surfaces of first and third transducer beamportions 1106, 1110 and/or strain gages 1138 can be mounted at bothopposed side surfaces of the second and fourth transducer beam portions1108, 1112. Similarly, strain gages 1140 can be mounted at both the topsurface and the bottom surface of the second and fourth transducer beamportions 1108, 1112. These strain gages 1136, 1138, 1140 measure forceeither by bending moment or difference of bending moments at two crosssections. As force is applied to the central body portion 1102 of theload transducer 1100, the transducer beam portions bend. This bendingeither stretches or compresses the strain gages 1136, 1138, 1140, whichin turn changes the resistance of the electrical current passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force, as applied to thecentral body portion 1102 of the load transducer 1100. In theillustrated embodiment, each of the strain gages 1136, 1138, 1140comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1136, 1138, 1140 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIGS. 39 and 41 of the illustrated embodiment, it canbe seen that the central body portion 1102 of the load transducer 1100comprises a plurality of mounting apertures 1142 (e.g., four apertures1142 arranged in 2×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1100 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43 ). Also, asdepicted in FIGS. 39 and 41 , the second and fourth transducer beamportions 1108, 1112 of the load transducer 1100 each comprise a mountingaperture 1144 (e.g., a single aperture 1144) disposed therethrough nearthe respective free ends 1108 a, 1112 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1100 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1100 is conveyedthrough the plurality of beam portions 1106, 1108, 1110, 1112 of theload transducer 1100 from the first object (e.g., the plate component1152 in FIGS. 42 and 43 ) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 39-41 , it can be seen that thecentral body portion 1102 of the load transducer 1100 comprises no otherapertures besides the mounting apertures 1142. That is, the central bodyportion 1102 is completely solid, except for the mounting apertures1142. Advantageously, the solid central body portion 1102 of the loadtransducer 1100 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1100 is mounted(e.g., plate component 1152—see FIGS. 42 and 43 ) without undergoingexcessive deformation (i.e., without undergoing non-elasticdeformation).

An exemplary embodiment of a force measurement system is illustrated inFIGS. 42 and 43 . In the illustrative embodiment, referring to FIG. 42 ,the force measurement system generally comprises a force measurementassembly 1150 (i.e., a force plate) that is operatively coupled to adata acquisition/data processing device 1174 (i.e., a data acquisitionand processing device or computing device that is capable of collecting,storing, and processing data). The force measurement assembly 1150illustrated in FIGS. 42 and 43 is configured to receive a subjectthereon, and is capable of measuring the forces and/or moments appliedto its measurement surface by the subject.

As shown in FIG. 42 , the data acquisition and processing device 1174(e.g., in the form of a laptop digital computer) generally includes abase portion 1178 with a central processing unit (CPU) disposed thereinfor collecting and processing the data that is received from the forcemeasurement assembly 1150, and a plurality of devices 1180-1184operatively coupled to the central processing unit (CPU) in the baseportion 1178. Preferably, the devices that are operatively coupled tothe central processing unit (CPU) comprise user input devices 1180, 1182in the form of a keyboard 1180 and a touchpad 1182, as well as agraphical user interface in the form of a laptop LCD screen 1184. Whilea laptop type computing system is depicted in the embodiment of FIG. 42, one of ordinary skill in the art will appreciate that another type ofdata acquisition and processing device 1174 can be substituted for thelaptop computing system such as, but not limited to, a palmtop computingdevice (i.e., a PDA) or a desktop type computing system having aplurality of separate, operatively coupled components (e.g., a desktoptype computing system including a main housing with a central processingunit (CPU) and data storage devices, a remote monitor, a remotekeyboard, and a remote mouse).

As illustrated in FIG. 42 , force measurement assembly 1150 isoperatively coupled to the data acquisition/data processing device 1174by virtue of an electrical cable 1176. In one embodiment of theinvention, the electrical cable 1176 is used for data transmission, aswell as for providing power to the force measurement assembly 1150.Various types of data transmission cables can be used for cable 1176.For example, the cable 1176 can be a Universal Serial Bus (USB) cable oran Ethernet cable. Preferably, the electrical cable 1176 contains aplurality of electrical wires bundled together, with at least one wirebeing used for power and at least another wire being used fortransmitting data. The bundling of the power and data transmission wiresinto a single electrical cable 1176 advantageously creates a simpler andmore efficient design. In addition, it enhances the safety of thetesting environment when human subjects are being tested on the forcemeasurement assembly 1150. However, it is to be understood that theforce measurement assembly 1150 can be operatively coupled to the dataacquisition/data processing device 1176 using other signal transmissionmeans, such as a wireless data transmission system. If a wireless datatransmission system is employed, it is preferable to provide the forcemeasurement assembly 1150 with a separate power supply in the form of aninternal power supply or a dedicated external power supply.

Referring again to FIG. 42 , it can be seen that the force measurementassembly 1150 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1152 supported on a pluralityof load transducers 1100. As shown in FIGS. 42 and 43 , the platecomponent 1152 comprises a top measurement surface 1154 (i.e., a planartop surface), a bottom surface 1164 disposed generally opposite to thetop measurement surface 1154, and a plurality of side surfaces 1156,1158, 1160, 1162 disposed between the top and bottom surfaces 1154,1164. In the illustrated embodiment, the first side surface 1156 of theplate component 1152 is disposed generally parallel to the second sidesurface 1158, and is disposed generally perpendicular to both the thirdside surface 1160 and the fourth side surface 1162. The third sidesurface 1160 of the plate component 1152 is disposed generally parallelto the fourth side surface 1162, and is disposed generally perpendicularto both the first side surface 1156 and the second side surface 1158.Turning to the exploded view of FIG. 43 , it can be seen that the bottomsurface 1164 of the plate component 1152 comprises a plurality ofL-shaped transducer recesses 1166 formed therein. Each of the pluralityof transducer recesses 1166 corresponding to a footprint of either firstand second beam portions 1106, 1108 or third and fourth beam portions1110, 1112 of one of the plurality of load transducers 1100 so that theload measuring portions of the transducer beam portions 1106, 1108,1110, 1112 with strain gages 1136, 1138, 1140 are spaced apart frombottom surface of the plate component 1152 (i.e., so that the entireload is transferred through the transducer beam portions 1106, 1108,1110, 1112). Advantageously, the compact footprint of the loadtransducer 1100 enables the narrow force plate 1150 to be capable ofmeasuring all three components of the force (i.e., F_(X), F_(Y), F_(Z))applied to the plate component 1152 thereof.

In illustrated embodiment of FIGS. 42 and 43 , the force measurementassembly 1150 comprises two (2) load transducers that are disposedunderneath, and near opposite ends of the plate component 1152.Advantageously, because the load transducers 1100 are compact, neitherof the load transducers 1100 extends substantially an entire length ofthe plate component 1152 of the force measurement assembly 1150. Thecompact construction of the load transducers 1100 not only reducesmaterial costs because less material is used to form the loadtransducers 1100, but it also allows the load transducers 1100 to beuniversally used on force plates having a myriad of different lengthsbecause it is not necessary for the load transducers 1100 to conform tothe footprint size of the force plate.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1150 having a plate component 1152 with a singlemeasurement surface 1154, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1150illustrated in FIGS. 42 and 43 , the dual force plate comprises twoseparate plate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on two (2) load transducers 1100 (i.e., load transducers1100 are disposed at opposite ends of each of the two plate components).As such, the dual force plate comprises a total of four (4) loadtransducers 1100 (i.e., two (2) load transducers 1100 under each of thetwo plate components).

Now, turning to FIG. 37 , it can be seen that the data acquisition/dataprocessing device 1174 (i.e., the laptop computing device) of the forcemeasurement system comprises a microprocessor 1174 a for processingdata, memory 1174 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1174 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 37 , theforce measurement assembly 1150 and the visual display device 1184 areoperatively coupled to the core components 1174 a, 1174 b, 1174 c of thedata acquisition/data processing device 1174 such that data is capableof being transferred between these devices 1150, 1174 a, 1174 b, 1174 c,and 1184. Also, as illustrated in FIG. 37 , a plurality of data inputdevices 1180, 1182 such as the keyboard 1180 and mouse 1182 shown inFIG. 42 , are operatively coupled to the core components 1174 a, 1174 b,1174 c of the data acquisition/data processing device 1174 so that auser is able to enter data into the data acquisition/data processingdevice 1174. In some embodiments, the data acquisition/data processingdevice 1174 can be in the form of a laptop computer, while in otherembodiments, the data acquisition/data processing device 1174 can beembodied as a desktop computer.

FIG. 38 graphically illustrates the acquisition and processing of theload data carried out by the exemplary force measurement system of FIG.42 . Initially, as shown in FIG. 38 , a load L is applied to the forcemeasurement assembly 1150 (e.g., by a subject disposed thereon). Theload is transmitted from the plate component 1152 to the loadtransducers 1100 disposed at each of the opposed ends of the platecomponent 1152. As described above, in the illustrated embodiment, eachof the load transducers 1100 includes a plurality of strain gages 1136,1138, 1140 wired in one or more Wheatstone bridge configurations,wherein the electrical resistance of each strain gage is altered whenthe associated beam portion of the load transducer 1100 undergoesdeformation resulting from the load (i.e., forces and/or moments) actingon the plate component 1152. For each plurality of strain gages disposedon the load transducers 1100, the change in the electrical resistance ofthe strain gages brings about a consequential change in the outputvoltage of the Wheatstone bridge (i.e., a quantity representative of theload being applied to the measurement surface 1154). Thus, in oneembodiment, the two (2) load transducers 1100 disposed under the platecomponent 1152 output a total of six (6) analog output voltages(signals). In some embodiments, the six (6) analog output voltages fromload transducers 1100 disposed under the plate component 1152 are thentransmitted to a preamplifier board (not shown) for preconditioning. Thepreamplifier board is used to increase the magnitudes of the transduceranalog voltages, and preferably, to convert the analog voltage signalsinto digital voltage signals as well. After which, the force measurementassembly 1150 transmits the force plate output signals S_(FP01)-S_(FP06)to a main signal amplifier/converter 1072. Depending on whether thepreamplifier board also includes an analog-to-digital (A/D) converter,the force plate output signals S_(FPO1)-S_(FP6) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 1072 further magnifies the force plate outputsignals S_(FPO1)-S_(FP06), and if the signals S_(FPO1)-S_(FP06) are ofthe analog-type (for a case where the preamplifier board did not includean analog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 1072transmits either the digital or analog signals S_(ACO1)-S_(AC06) to thedata acquisition/data processing device 1174 (computer 1174) so that theforces and/or moments that are being applied to the measurement surface1154 of the force measurement assembly 1150 can be transformed intooutput load values OL. In addition to the components 1174 a, 1174 b,1174 c, the data acquisition/data processing device 1174 may furthercomprise an analog-to-digital (A/D) converter if the signalsS_(AC01)-S_(AC06) are in the form of analog signals. In such a case, theanalog-to-digital converter will convert the analog signals into digitalsignals for processing by the microprocessor 1174 a.

When the data acquisition/data processing device 1174 receives thevoltage signals S_(ACO1)-S_(AC06), it initially transforms the signalsinto output forces by multiplying the voltage signals S_(ACO1)-S_(AC06)by a calibration matrix. If a load transducer having moment strain gages(as shown in FIGS. 51-54 ) is used in conjunction with the forcemeasurement assembly 1150, the data acquisition/data processing devicemay additionally transform the signals into output moments bymultiplying the voltage signals by the calibration matrix. After which,the force exerted on the surface 1154 of the force measurement assembly1150, and the center of pressure of the applied force (i.e., the x and ycoordinates of the point of application of the force applied to themeasurement surface 1154) is determined by the data acquisition/dataprocessing device 1174. Referring to the perspective view of FIG. 42 ,it can be seen that the center of pressure coordinates (x_(P) _(L) ,y_(P) _(L) ) for the plate component 1152 of the force measurementassembly 1150 are determined in accordance with x and y coordinate axes1168, 1170. In FIG. 42 , the vertical component of the force (F_(Z)) isdefined by the z coordinate axis 1172.

In one exemplary embodiment, the data acquisition/data processing device1174 determines all three (3) orthogonal components of the resultantforces acting on the plate component 1152 of the force measurementassembly 1150 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments ofthe invention, all three (3) orthogonal components of the resultantforces and moments acting on the plate component 1152 of the forcemeasurement assembly 1150 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y),M_(Z)) may be determined (i.e., when the load transducer 1400 is used inlieu of the load transducers 1100).

FIGS. 44-46 illustrate a load transducer 1200 according to a fourteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 44 , it can be seen that the loadtransducer 1200 generally includes a one-piece compact transducer frame1204 having a central body portion 1202 and a plurality of beam portions1206, 1208, 1210, 1212 extending along sides 1202 a, 1202 b, 1202 c ofthe central body portion 1202. As best illustrated in the perspectiveview of FIG. 44 , each of the beam portions 1206, 1208, 1210, 1212comprises one or more load cells or transducer elements for measuringforces and/or moments.

With reference again to FIG. 44 , it can be seen that the illustratedcentral body portion 1202 is generally in the form of a rectangularprism with substantially right angle corners (i.e., substantially 90degree corners). In FIG. 44 , it can be seen that the body portion 1202comprises a first pair of opposed sides 1202 a, 1202 c and a second pairof opposed sides 1202 b, 1202 d. The side 1202 a is disposed generallyparallel to the side 1202 c, while the side 1202 b is disposed generallyparallel to the side 1202 d. Each of the sides 1202 a, 1202 b, 1202 c,1202 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1202. Also, each of the first pair ofopposed sides 1202 a, 1202 c is disposed generally perpendicular to eachof the second pair of opposed sides 1202 b, 1202 d. In addition, asshown in FIG. 44 , the second side 1202 b comprises a beam connectingportion 1214 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1214 connects the beamportions 1206 and 1210 to the second side 1202 b of the central bodyportion 1202. In the illustrated embodiment, the total load applied tothe load transducer 1200 is transmitted through the beam portions 1206,1208, 1210, 1212.

As best shown in FIGS. 44 and 46 , the proximal end of the first beamportion 1206 is rigidly connected to the central body portion 1202 bymeans of the beam connecting portion 1214, and the distal end of thefirst beam portion 1206 is rigidly connected to the proximal end of thesecond beam portion 1208. As depicted in these figures, the first beamportion 1206 extends along the second side 1202 b of the central bodyportion 1202, and the second beam portion 1208 extends along the firstside 1202 a of the central body portion 1202. More particularly, in theillustrative embodiment, the longitudinal axis of the first beam portion1206 is disposed generally parallel to the second side 1202 b of thecentral body portion 1202, and the longitudinal axis of the second beamportion 1208 is disposed generally parallel to the first side 1202 a ofthe central body portion 1202. As best shown in the perspective view ofFIG. 44 , the top and bottom surfaces of each of the first and secondbeam portions 1206, 1208 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1202. Also, in theillustrative embodiment, with reference again to FIGS. 44 and 46 , thefirst beam portion 1206 is generally perpendicular, or perpendicular tothe second beam portion 1208 (i.e., together the first and second beamportions 1206, 1208 form an overall L-shaped beam arm). In addition, asshown in these figures, the first beam portion 1206 is spaced apart fromthe second side 1202 b of the central body portion 1202 by a first gap1228, and the second beam portion 1208 is spaced apart from the firstside 1202 a of the central body portion 1202 by a second gap 1230. Inthe illustrative embodiment, together the first gap 1228 and the secondgap 1230 form an overall L-shaped gap (i.e., the first gap 1228 isdisposed perpendicular to the second gap 1230).

Also, referring again to FIGS. 44 and 46 , it can be seen that theproximal end of the third beam portion 1210 is rigidly connected to thecentral body portion 1202 by means of the beam connecting portion 1214,and the distal end of the third beam portion 1210 is rigidly connectedto the proximal end of the fourth beam portion 1212. As depicted inthese figures, the third beam portion 1210 extends along the second side1202 b of the central body portion 1202, and the fourth beam portion1212 extends along the third side 1202 c of the central body portion1202. More particularly, in the illustrative embodiment, thelongitudinal axis of the third beam portion 1210 is disposed generallyparallel to the second side 1202 b of the central body portion 1202, andthe longitudinal axis of the fourth beam portion 1212 is disposedgenerally parallel to the third side 1202 c of the central body portion1202. As best shown in the perspective view of FIG. 44 , the top andbottom surfaces of each of the third and fourth beam portions 1210, 1212are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1202. Also, in the illustrative embodiment,with reference again to FIGS. 44 and 46 , the third beam portion 1210 isgenerally perpendicular, or perpendicular to the fourth beam portion1212 (i.e., together the third and fourth beam portions 1210, 1212 forman overall L-shaped beam arm). In addition, as shown in these figures,the third beam portion 1210 is spaced apart from the second side 1202 bof the central body portion 1202 by a third gap 1232, and the fourthbeam portion 1212 is spaced apart from the third side 1202 c of thecentral body portion 1202 by a fourth gap 1234. In the illustrativeembodiment, together the third gap 1232 and the fourth gap 1234 form anoverall L-shaped gap (i.e., the third gap 1232 is disposed perpendicularto the fourth gap 1234).

In the illustrative embodiment of FIGS. 44 and 46 , unlike theembodiment of FIGS. 39-41 , it can be seen that the free end 1208 a ofthe second beam portion 1208 is spaced apart from the fourth side 1202 dof the central body portion 1202 (i.e., the second beam portion 1208extends beyond the fourth side 1202 d of the central body portion 1202).Also, as shown in FIGS. 44 and 46 , the free end 1212 a of the fourthbeam portion 1212 is spaced apart from the fourth side 1202 d of thecentral body portion 1202 (i.e., the fourth beam portion 1212 extendsbeyond the fourth side 1202 d of the central body portion 1202).

In the illustrative embodiment of FIGS. 44-46 , the first beam portion1206 is provided with an aperture 1216 disposed therethrough, the secondbeam portion 1208 is provided with apertures 1218, 1220 disposedtherethrough, the third beam portion 1210 is provided with an aperture1222 disposed therethrough, and the fourth beam portion 1212 is providedwith apertures 1224, 1226 disposed therethrough. In particular, thefirst and third transducer beam portions 1206, 1210 are provided withrespective generally rectangular apertures 1216, 1222 disposedvertically through the beam portions 1206, 1210. The second transducerbeam portion 1208 is provided with a first generally rectangularaperture 1218 disposed vertically through the beam portion 1208 and asecond generally rectangular aperture 1220 disposed horizontally throughthe beam portion 1208. As such, the vertically extending aperture 1218of the second beam portion 1208 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1220. Similarly, the fourth transducerbeam portion 1212 is provided with a first generally rectangularaperture 1224 disposed vertically through the beam portion 1212 and asecond generally rectangular aperture 1226 disposed horizontally throughthe beam portion 1212. As such, the vertically extending aperture 1224of the fourth beam portion 1212 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1226. The apertures 1216, 1218, 1220,1222, 1224, 1226, which are disposed through the transducer beamportions 1206, 1208, 1210, 1212, significantly increase the sensitivityof the load transducer 1200 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1206, 1208,1210, 1212 at the locations of the apertures 1216, 1218, 1220, 1222,1224, 1226.

As best shown in the perspective view of FIG. 44 , the illustrated loadcells are located on the transducer beam portions 1206, 1208, 1210,1212. In the illustrated embodiment, each load cell comprises one ormore strain gages 1236, 1238, 1240. Specifically, in the illustratedembodiment, the first transducer beam portion 1206 of the loadtransducer 1200 comprises a strain gage 1236 disposed on a side surfacethereof that is sensitive to a first shear force component (i.e., aF_(Y) strain gage) and substantially centered on the aperture 1216. Inthe illustrated embodiment, the second transducer beam portion 1208 ofthe load transducer 1200 comprises a strain gage 1238 disposed on a sidesurface thereof that is sensitive to a second shear force component(i.e., a F_(X) strain gage) and substantially centered on the aperture1218. The second transducer beam portion 1208 also comprises a straingage 1240 disposed on a top surface thereof that is sensitive to avertical force component (i.e., a F_(Z) strain gage) and substantiallycentered on the aperture 1220. Also, in the illustrative embodiment, thethird transducer beam portion 1210 of the load transducer 1200 comprisesa strain gage 1236 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1222. The fourth transducer beamportion 1212 of the load transducer 1200 comprises a strain gage 1238disposed on a side surface thereof that is sensitive to a second shearforce component (i.e., a F_(X) strain gage) and substantially centeredon the aperture 1224. The fourth transducer beam portion 1212 alsocomprises a strain gage 1240 disposed on a top surface thereof that issensitive to a vertical force component (i.e., a F_(Z) strain gage) andsubstantially centered on the aperture 1226. In the illustratedembodiment, the first shear force component is generally perpendicularto the second shear force component, and each of the first and secondshear force components are generally perpendicular to the vertical forcecomponent.

In the illustrated embodiment, the strain gages 1236, 1238, 1240 aredisposed on respective outer surfaces of the transducer beam portions1206, 1208, 1210, 1212. The outer surfaces of the transducer beamportions 1206, 1208, 1210, 1212 on which the strain gages 1236, 1238,1240 are disposed are generally opposite to the inner surfaces of therespective apertures 1216, 1218, 1220, 1222, 1224, 1226.

As best shown in FIGS. 44-46 , the illustrated load cells are mounted onthe top and outer side surfaces of the transducer beam portions 1206,1208, 1210, 1212 of the load transducer 1200. Alternatively, the straingages 1236, 1238 can be mounted to the inner side surfaces of therespective first and second transducer beam portions 1206, 1208, ratherthan to the outer side surfaces of the respective first and secondtransducer beam portions 1206, 1208 as illustrated in FIGS. 44 and 45 .Similarly, the strain gages 1236, 1238 can be mounted to the inner sidesurfaces of the respective third and fourth transducer beam portions1210, 1212, rather than to the outer side surfaces of the respectivethird and fourth transducer beam portions 1210, 1212 as illustrated inFIGS. 44 and 46 . In addition, the strain gages 1240 can be mounted tothe bottom surfaces of the second and fourth transducer beam portions1208, 1212, rather than to the top of the transducer beam portions 1208,1212 as illustrated in FIGS. 44 and 45 . In general, the strain gages1236, 1238, 1240 are mounted to surfaces generally normal to thedirection of applied vertical and/or shear forces (i.e., F_(X), F_(Y),F_(Z)). It is also noted that alternatively, strain gages 1236 can bemounted at both opposed side surfaces of first and third transducer beamportions 1206, 1210 and/or strain gages 1238 can be mounted at bothopposed side surfaces of the second and fourth transducer beam portions1208, 1212. Similarly, strain gages 1240 can be mounted at both the topsurface and the bottom surface of the second and fourth transducer beamportions 1208, 1212. These strain gages 1236, 1238, 1240 measure forceeither by bending moment or difference of bending moments at two crosssections. As force is applied to the central body portion 1202 of theload transducer 1200, the transducer beam portions bend. This bendingeither stretches or compresses the strain gages 1236, 1238, 1240, whichin turn changes the resistance of the electrical current passingtherethrough. The amount of change in the electrical voltage or currentis proportional to the magnitude of the applied force, as applied to thecentral body portion 1202 of the load transducer 1200. In theillustrated embodiment, each of the strain gages 1236, 1238, 1240comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1236, 1238, 1240 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIGS. 44 and 46 of the illustrated embodiment, it canbe seen that the central body portion 1202 of the load transducer 1200comprises a plurality of mounting apertures 1242 (e.g., six apertures1242 arranged in 3×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1200 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43 ). Also, asdepicted in FIGS. 44 and 46 , the second and fourth transducer beamportions 1208, 1212 of the load transducer 1200 each comprise a mountingaperture 1244 (e.g., a single aperture 1244) disposed therethrough nearthe respective free ends 1208 a, 1212 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1200 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1200 is conveyedthrough the plurality of beam portions 1206, 1208, 1210, 1212 of theload transducer 1200 from the first object (e.g., the plate component1152 in FIGS. 42 and 43 ) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 44-46 , it can be seen that thecentral body portion 1202 of the load transducer 1200 comprises no otherapertures besides the mounting apertures 1242. That is, the central bodyportion 1202 is completely solid, except for the mounting apertures1242. Advantageously, the solid central body portion 1202 of the loadtransducer 1200 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1100 is mounted(e.g., plate component of a force measurement assembly) withoutundergoing excessive deformation (i.e., without undergoing non-elasticdeformation).

FIGS. 47 and 48 illustrate a load transducer 1300, 1300′ according to afifteenth exemplary embodiment of the present invention. Referring tothe perspective view of FIG. 47 , it can be seen that the loadtransducer 1300 generally includes a one-piece compact transducer frame1304 having a central body portion 1302 and a plurality of beam portions1306, 1308 extending along sides 1302 a, 1302 b of the central bodyportion 1302. As best illustrated in the perspective view of FIG. 47 ,each of the beam portions 1306, 1308 comprises one or more load cells ortransducer elements for measuring forces and/or moments. The loadtransducer 1300 in FIG. 47 is configured for a left side mountingarrangement on a force measurement assembly (e.g., the force measurementassembly 1340 in FIGS. 49 and 50 ), whereas the load transducer 1300′ inFIG. 48 is configured for a right side mounting arrangement on a forcemeasurement assembly (e.g., the force measurement assembly 1340 in FIGS.49 and 50 ). Other than being configured for mounting on different sidesof a force measurement assembly, the load transducers 1300, 1300′ inFIGS. 47 and 48 are generally the same.

With reference again to FIG. 47 , it can be seen that the illustratedcentral body portion 1302 is generally in the form of a rectangularprism with substantially right angle corners (i.e., substantially 90degree corners). In FIG. 47 , it can be seen that the body portion 1302comprises a first pair of opposed sides 1302 a, 1302 c and a second pairof opposed sides 1302 b, 1302 d. The side 1302 a is disposed generallyparallel to the side 1302 c, while the side 1302 b is disposed generallyparallel to the side 1302 d. Each of the sides 1302 a, 1302 b, 1302 c,1302 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1302. Also, each of the first pair ofopposed sides 1302 a, 1302 c is disposed generally perpendicular to eachof the second pair of opposed sides 1302 b, 1302 d. In addition, asshown in FIG. 47 , the second side 1302 b comprises a beam connectingportion 1310 extending outward therefrom. In the illustrated embodiment,it can be seen that the beam connecting portion 1310 connects the firstbeam portion 1306 to the second side 1302 b of the central body portion1302. In the illustrated embodiment, the total load applied to the loadtransducer 1300 is transmitted through the beam portions 1306, 1308.

As best shown in FIG. 47 , the proximal end of the first beam portion1306 is rigidly connected to the central body portion 1302 by means ofthe beam connecting portion 1310, and the distal end of the first beamportion 1306 is rigidly connected to the proximal end of the second beamportion 1308. As depicted in these figures, the first beam portion 1306extends along the second side 1302 b of the central body portion 1302,and the second beam portion 1308 extends along the first side 1302 a ofthe central body portion 1302. More particularly, in the illustrativeembodiment, the longitudinal axis of the first beam portion 1306 isdisposed generally parallel to the second side 1302 b of the centralbody portion 1302, and the longitudinal axis of the second beam portion1308 is disposed generally parallel to the first side 1302 a of thecentral body portion 1302. As best shown in the perspective view of FIG.47 , the top and bottom surfaces of each of the first and second beamportions 1306, 1308 are disposed substantially co-planar with the topand bottom surfaces of the central body portion 1302. Also, in theillustrative embodiment, with reference again to FIG. 47 , the firstbeam portion 1306 is generally perpendicular, or perpendicular to thesecond beam portion 1308 (i.e., together the first and second beamportions 1306, 1308 form an overall L-shaped beam arm). In addition, asshown in this figure, the first beam portion 1306 is spaced apart fromthe second side 1302 b of the central body portion 1302 by a first gap1318, and the second beam portion 1308 is spaced apart from the firstside 1302 a of the central body portion 1302 by a second gap 1320. Inthe illustrative embodiment, together the first gap 1318 and the secondgap 1320 form an overall L-shaped gap (i.e., the first gap 1318 isdisposed perpendicular to the second gap 1320). As shown in FIG. 48 ,the first and second beam portions 1306′, 1308′ have the sameconfiguration as the first and second beam portions 1306, 1308, exceptthat the beam portions 1306′, 1308′ of the load transducer 1300′ areconfigured for a right side mounting arrangement on a force measurementassembly, rather than the left side mounting arrangement of the loadtransducer 1300.

In the illustrative embodiment of FIG. 47 , like the embodiment of FIGS.39-41 , it can be seen that the free end 1308 a of the second beamportion 1308 is generally aligned, or aligned with the fourth side 1302d of the central body portion 1302 (i.e., the end face of the secondbeam portion 1308 is co-planar with the fourth side 1302 d of thecentral body portion 1302). Similarly, as shown in FIG. 48 , the freeend 1308 a′ of the second beam portion 1308′ of the load transducer1300′ is generally aligned, or aligned with the fourth side 1302 d ofthe central body portion 1302 (i.e., the end face of the second beamportion 1308′ is co-planar with the fourth side 1302 d of the centralbody portion 1302).

In the illustrative embodiment of FIG. 47 , the first beam portion 1306is provided with an aperture 1312 disposed therethrough, and the secondbeam portion 1308 is provided with apertures 1314, 1316 disposedtherethrough. In particular, the first transducer beam portion 1306 isprovided with a generally rectangular aperture 1312 disposed verticallythrough the beam portion 1306. The second transducer beam portion 1308is provided with a first generally rectangular aperture 1314 disposedvertically through the beam portion 1308 and a second generallyrectangular aperture 1316 disposed horizontally through the beam portion1308. As such, the vertically extending aperture 1314 of the second beamportion 1308 extends in a direction that is generally perpendicular, orperpendicular to the extending direction of the horizontally extendingaperture 1316. The apertures 1312, 1314, 1316, which are disposedthrough the transducer beam portions 1306, 1308, significantly increasethe sensitivity of the load transducer 1300 when a load is appliedthereto by reducing the cross-sectional area of the transducer beamportions 1306, 1308 at the locations of the apertures 1312, 1314, 1316.

As best shown in the perspective view of FIG. 47 , the illustrated loadcells are located on the transducer beam portions 1306, 1308. In theillustrated embodiment, each load cell comprises one or more straingages 1322, 1324, 1326. Specifically, in the illustrated embodiment, thefirst transducer beam portion 1306 of the load transducer 1300 comprisesa strain gage 1322 disposed on a side surface thereof that is sensitiveto a first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1312. In the illustratedembodiment, the second transducer beam portion 1308 of the loadtransducer 1300 comprises a strain gage 1324 disposed on a side surfacethereof that is sensitive to a second shear force component (i.e., aF_(X) strain gage) and substantially centered on the aperture 1314. Thesecond transducer beam portion 1308 also comprises a strain gage 1326disposed on a top surface thereof that is sensitive to a vertical forcecomponent (i.e., a F_(Z) strain gage) and substantially centered on theaperture 1316. In the illustrated embodiment, the first shear forcecomponent is generally perpendicular to the second shear forcecomponent, and each of the first and second shear force components aregenerally perpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1322, 1324, 1326 aredisposed on respective outer surfaces of the transducer beam portions1306, 1308. The outer surfaces of the transducer beam portions 1306,1308 on which the strain gages 1322, 1324, 1326 are disposed aregenerally opposite to the inner surfaces of the respective apertures1312, 1314, 1316.

As best shown in FIG. 47 , the illustrated load cells are mounted on thetop and outer side surfaces of the transducer beam portions 1306, 1308of the load transducer 1300. Alternatively, the strain gages 1322, 1324can be mounted to the inner side surfaces of the respective first andsecond transducer beam portions 1306, 1308, rather than to the outerside surfaces of the respective first and second transducer beamportions 1306, 1308 as illustrated in FIG. 47 . In addition, the straingage 1326 can be mounted to the bottom surface of the second transducerbeam portion 1308, rather than to the top of the transducer beam portion1308 as illustrated in FIG. 47 . In general, the strain gages 1322,1324, 1326 are mounted to surfaces generally normal to the direction ofapplied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). It isalso noted that alternatively, strain gages 1322 can be mounted at bothopposed side surfaces of first transducer beam portion 1306 and/orstrain gages 1324 can be mounted at both opposed side surfaces of thesecond transducer beam portion 1308. Similarly, strain gages 1326 can bemounted at both the top surface and the bottom surface of the secondtransducer beam portion 1308. These strain gages 1322, 1324, 1326measure force either by bending moment or difference of bending momentsat two cross sections. As force is applied to the central body portion1302 of the load transducer 1300, the transducer beam portions bend.This bending either stretches or compresses the strain gages 1322, 1324,1326, which in turn changes the resistance of the electrical currentpassing therethrough. The amount of change in the electrical voltage orcurrent is proportional to the magnitude of the applied force, asapplied to the central body portion 1302 of the load transducer 1300. Inthe illustrated embodiment, each of the strain gages 1322, 1324, 1326comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration). In analternative embodiment, each of the strain gages 1322, 1324, 1326 maycomprise a half-bridge strain gage configuration (i.e., two (2) activestrain gage elements wired in a Wheatstone bridge configuration).

Turning again to FIG. 47 of the illustrated embodiment, it can be seenthat the central body portion 1302 of the load transducer 1300 comprisesa plurality of mounting apertures 1328 (e.g., four apertures 1328arranged in 2×2 array) disposed therethrough for accommodating fasteners(e.g., screws) that attach the load transducer 1300 to a first object,such as a plate component of a force plate or force measurement assembly(e.g., plate component 1342 in FIGS. 49 and 50 ). Also, as depicted inFIG. 47 , the second transducer beam portion 1308 of the load transducer1300 comprises a mounting aperture 1330 (e.g., a single aperture 1330)disposed therethrough near the free end 1308 a thereof for accommodatinga fastener (e.g., a screw) that attaches the load transducer 1300 to asecond object, such as a mounting foot of a force plate or forcemeasurement assembly. The load applied to the load transducer 1300 isconveyed through the plurality of beam portions 1306, 1308 of the loadtransducer 1300 from the first object (e.g., the plate component 1342 inFIGS. 49 and 50 ) to the second object (e.g., the mounting foot of theforce measurement assembly).

In the illustrative embodiments of FIGS. 47 and 48 , it can be seen thatthe central body portions 1302 of the load transducers 1300, 1300′comprise no other apertures besides the mounting apertures 1328. Thatis, the central body portion 1302 is completely solid, except for themounting apertures 1328. Advantageously, the solid central body portion1302 of the load transducer 1300, 1300′ is structurally robust enough tosupport the load being applied to the object to which the loadtransducer 1300, 1300′ is mounted (e.g., plate component 1342—see FIGS.49 and 50 ) without undergoing excessive deformation (i.e., withoutundergoing non-elastic deformation).

An exemplary embodiment of a force measurement assembly 1340 isillustrated in FIGS. 49 and 50 . In the illustrative embodiment, theforce measurement assembly 1340 of FIGS. 49 and 50 may be provided aspart of a force measurement system, and thus may be operatively coupledto a data acquisition/data processing device (i.e., the dataacquisition/data processing device 1174 described in conjunction withFIG. 42 above). The functionality of the force measurement systemcomprising the force measurement assembly 1340 and the dataacquisition/data processing device would be generally the same as thatdescribed above for the embodiment of FIGS. 42 and 43 , and thus neednot be reiterated in conjunction with the description of the forcemeasurement assembly 1340 of FIGS. 49 and 50 . Also, like the forcemeasurement assembly 1150 described above, the force measurementassembly 1340 illustrated in FIGS. 49 and 50 is configured to receive asubject thereon, and is capable of measuring the forces and/or momentsapplied to its measurement surface by the subject.

Referring again to FIG. 49 , it can be seen that the force measurementassembly 1340 of the illustrated embodiment is in the form of a forceplate assembly with a single, continuous measurement surface. The forceplate assembly includes a plate component 1342 supported on a pluralityof load transducers 1300, 1300′. As shown in FIGS. 49 and 50 , the platecomponent 1342 comprises a top measurement surface 1344 (i.e., a planartop surface), a bottom surface 1354 disposed generally opposite to thetop measurement surface 1344, and a plurality of side surfaces 1346,1348, 1350, 1352 disposed between the top and bottom surfaces 1344,1354. In the illustrated embodiment, the first side surface 1346 of theplate component 1342 is disposed generally parallel to the second sidesurface 1348, and is disposed generally perpendicular to both the thirdside surface 1350 and the fourth side surface 1352. The third sidesurface 1350 of the plate component 1342 is disposed generally parallelto the fourth side surface 1352, and is disposed generally perpendicularto both the first side surface 1346 and the second side surface 1348.Turning to the exploded view of FIG. 50 , it can be seen that the bottomsurface 1354 of the plate component 1342 comprises a plurality ofL-shaped transducer recesses 1356 formed therein. Each of the pluralityof transducer recesses 1356 corresponds to a footprint of the first andsecond beam portions 1306, 1308 of one of the plurality of loadtransducers 1300, 1300′ so that the load measuring portions of thetransducer beam portions 1306, 1308 with strain gages 1322, 1324, 1326are spaced apart from a bottom surface of the plate component 1342(i.e., so that the entire load is transferred through the transducerbeam portions 1306, 1308).

In illustrated embodiment of FIGS. 49 and 50 , the force measurementassembly 1340 comprises a total of four (4) load transducers 1300, 1300′that are disposed underneath, and near each of the respective fourcorners (4) of the plate component 1342. As explained above, the loadtransducers 1300′ are generally the same as the load transducers 1300,expect that they are configured as a mirror image of the loadtransducers 1300. Advantageously, because the load transducers 1300,1300′ are compact, none of the plurality of load transducers 1300, 1300′extend substantially an entire length or width of the plate component1342 of the force measurement assembly 1340. The compact construction ofthe load transducers 1300, 1300′ not only reduces material costs becauseless material is used to form the load transducers 1300, 1300′, but italso allows the load transducers 1300, 1300′ to be universally used onforce plates having a myriad of different lengths and widths because itis not necessary for the load transducers 1300, 1300′ to conform to thefootprint size of the force plate.

In other embodiments of the invention, rather than using a forcemeasurement assembly 1340 having a plate component 1342 with a singlemeasurement surface 1344, it is to be understood that a forcemeasurement assembly in the form of a dual force plate may bealternatively employed. Unlike the single force plate assembly 1340illustrated in FIGS. 49 and 50 , the dual force plate comprises twoseparate plate components, each of which is configured to accommodate arespective one of a subject's feet thereon (i.e., the left platecomponent accommodates the subject's left foot, whereas the right platecomponent accommodates the subject's right foot). In these alternativeembodiments, each of the two plate components of the dual force plateare supported on four (4) load transducers 1300, 1300′ (i.e., a loadtransducer 1300, 1300′ is disposed in each of the respective four (4)corners of each of the two plate components). As such, the dual forceplate comprises a total of eight (8) load transducers 1300, 1300′ (i.e.,four (4) load transducers 1300, 1300′ under each of the two platecomponents).

Similar to that described above for the force measurement assembly 1150,the force measurement assembly 1340 of FIGS. 49 and 50 is capable ofmeasuring all three (3) orthogonal components of the resultant forcesacting on the plate component 1342 of the force measurement assembly1340 (i.e., F_(X), F_(Y), F_(Z)). In yet other embodiments of theinvention, all three (3) orthogonal components of the resultant forcesand moments acting on the plate component 1342 of the force measurementassembly 1340 (i.e., F_(X), F_(Y), F_(Z), M_(X), M_(Y), M_(Z)) may bedetermined (i.e., when the load transducer 1400 is used in lieu of theload transducers 1300, 1300′). Also, referring to the perspective viewof FIG. 49 , it can be seen that the center of pressure coordinates(x_(P) _(L) , y_(P) _(L) ) for the plate component 1342 of the forcemeasurement assembly 1340 may be determined in accordance with x and ycoordinate axes 1358, 1360. In FIG. 49 , the vertical component of theforce (F_(Z)) is defined by the z coordinate axis 1362.

FIGS. 51-54 illustrate a load transducer 1400 according to a sixteenthexemplary embodiment of the present invention. Referring initially tothe perspective view of FIG. 51 , it can be seen that the loadtransducer 1400 generally includes a one-piece compact transducer frame1404 having a central body portion 1402 and beam portions 1406, 1408,1410, 1412 disposed on opposite sides 1402 a, 1402 c of the central bodyportion 1402. As best illustrated in the perspective view of FIG. 51 ,each of the beam portions 1406, 1408, 1410, 1412 comprises one or moreload cells or transducer elements for measuring forces and/or moments.

With reference again to FIG. 51 , it can be seen that the illustratedcentral body portion 1402 is generally in the form of rectangular prismwith substantially right angle corners (i.e., substantially 90 degreecorners). In FIG. 51 , it can be seen that the body portion 1402comprises a first pair of opposed sides 1402 a, 1402 c and a second pairof opposed sides 1402 b, 1402 d. The side 1402 a is disposed generallyparallel to the side 1402 c, while the side 1402 b is disposed generallyparallel to the side 1402 d. Each of the sides 1402 a, 1402 b, 1402 c,1402 d is disposed generally perpendicular to the planar top and bottomsurfaces of the body portion 1402. Also, each of the first pair ofopposed sides 1402 a, 1402 c is disposed generally perpendicular to eachof the second pair of opposed sides 1402 b, 1402 d. In addition, asshown in FIG. 51 , the first beam portion 1406 extends from the firstside 1402 a of the central body portion 1402 and the third beam portion1410 extends from the third side 1402 c of the central body portion1402. In the illustrated embodiment, the total load applied to the loadtransducer 1400 is transmitted through the beam portions 1406, 1408,1410, 1412.

As best shown in FIGS. 51 and 54 , the proximal end of the first beamportion 1406 is rigidly connected to the first side 1402 a of thecentral body portion 1402, and the distal end of the first beam portion1406 is rigidly connected to the proximal end of the second beam portion1408. As depicted in these figures, the second beam portion 1408 extendsalong the first side 1402 a of the central body portion 1402. In theillustrative embodiment, the longitudinal axis of the first beam portion1406 is disposed generally perpendicular to the first side 1402 a of thecentral body portion 1402, and the longitudinal axis of the second beamportion 1408 is disposed generally parallel to the first side 1402 a ofthe central body portion 1402. As best shown in the perspective view ofFIG. 51 , the top and bottom surfaces of each of the first and secondbeam portions 1406, 1408 are disposed substantially co-planar with thetop and bottom surfaces of the central body portion 1402. Also, in theillustrative embodiment, with reference again to FIGS. 51 and 54 , thefirst beam portion 1406 is generally perpendicular, or perpendicular tothe second beam portion 1408 (i.e., together the first and second beamportions 1406, 1408 form an overall L-shaped beam arm). In addition, asshown in these figures, the second beam portion 1408 is spaced apartfrom the first side 1402 a of the central body portion 1402 by arectangular beam gap 1426.

Also, referring again to FIGS. 51 and 54 , it can be seen that theproximal end of the third beam portion 1410 is rigidly connected to thethird side 1402 c of the central body portion 1402, and the distal endof the third beam portion 1410 is rigidly connected to the proximal endof the fourth beam portion 1412. As depicted in these figures, thefourth beam portion 1412 extends along the third side 1402 c of thecentral body portion 1402. In the illustrative embodiment, thelongitudinal axis of the third beam portion 1410 is disposed generallyperpendicular to the third side 1402 c of the central body portion 1402,and the longitudinal axis of the fourth beam portion 1412 is disposedgenerally parallel to the third side 1402 c of the central body portion1402. As best shown in the perspective view of FIG. 51 , the top andbottom surfaces of each of the third and fourth beam portions 1410, 1412are disposed substantially co-planar with the top and bottom surfaces ofthe central body portion 1402. Also, in the illustrative embodiment,with reference again to FIGS. 51 and 54 , the third beam portion 1410 isgenerally perpendicular, or perpendicular to the fourth beam portion1412 (i.e., together the third and fourth beam portions 1410, 1412 forman overall L-shaped beam arm). In addition, as shown in these figures,the fourth beam portion 1412 is spaced apart from the third side 1402 cof the central body portion 1402 by a rectangular beam gap 1428.

In the illustrative embodiment of FIGS. 51-54 , like the embodiment ofFIGS. 39-41 , it can be seen that the free end 1408 a of the second beamportion 1408 is generally aligned, or aligned with the fourth side 1402d of the central body portion 1402 (i.e., the end face of the secondbeam portion 1408 is co-planar with the fourth side 1402 d of thecentral body portion 1402). Also, as shown in FIGS. 51 and 54 , the freeend 1412 a of the fourth beam portion 1412 is generally aligned, oraligned with the fourth side 1402 d of the central body portion 1402(i.e., the end face of the fourth beam portion 1412 is co-planar withthe fourth side 1402 d of the central body portion 1402).

In the illustrative embodiment of FIGS. 51-54 , the first beam portion1406 is provided with an aperture 1414 disposed therethrough, the secondbeam portion 1408 is provided with apertures 1416, 1418 disposedtherethrough, the third beam portion 1410 is provided with an aperture1420 disposed therethrough, and the fourth beam portion 1412 is providedwith apertures 1422, 1424 disposed therethrough. In particular, thefirst and third transducer beam portions 1406, 1410 are provided withrespective generally rectangular apertures 1414, 1420 disposedvertically through the beam portions 1406, 1410. The second transducerbeam portion 1408 is provided with a first generally rectangularaperture 1416 disposed vertically through the beam portion 1408 and asecond generally rectangular aperture 1418 disposed horizontally throughthe beam portion 1408. As such, the vertically extending aperture 1416of the second beam portion 1408 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1418. Similarly, the fourth transducerbeam portion 1412 is provided with a first generally rectangularaperture 1422 disposed vertically through the beam portion 1412 and asecond generally rectangular aperture 1424 disposed horizontally throughthe beam portion 1412. As such, the vertically extending aperture 1422of the fourth beam portion 1412 extends in a direction that is generallyperpendicular, or perpendicular to the extending direction of thehorizontally extending aperture 1424. The apertures 1414, 1416, 1418,1420, 1422, 1424, which are disposed through the transducer beamportions 1406, 1408, 1410, 1412, significantly increase the sensitivityof the load transducer 1400 when a load is applied thereto by reducingthe cross-sectional area of the transducer beam portions 1406, 1408,1410, 1412 at the locations of the apertures 1414, 1416, 1418, 1420,1422, 1424.

As best shown in the perspective view of FIG. 51 , the illustrated loadcells are located on the transducer beam portions 1406, 1408, 1410,1412. In the illustrated embodiment, each load cell comprises one ormore strain gages 1430, 1432, 1434, 1436 a, 1436 b, 1438 a, 1438 b, 1440a, 1440 b. Specifically, in the illustrated embodiment, the firsttransducer beam portion 1406 of the load transducer 1400 comprises astrain gage 1430 disposed on a side surface thereof that is sensitive toa first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1414. The first transducer beamportion 1406 also comprises a first set of strain gages 1438 a, 1438 bthat are sensitive to a first moment component (i.e., a M_(Y) straingages). The strain gages 1438 a, 1438 b are disposed on opposed top andbottom surfaces of the first transducer beam portion 1406, and aresubstantially vertically aligned with one another. The first transducerbeam portion 1406 additionally comprises a second set of strain gages1440 a, 1440 b that are sensitive to a second moment component (i.e., aM_(Z) strain gages). The strain gages 1440 a, 1440 b are disposed onopposed side surfaces of the first transducer beam portion 1406, and aresubstantially horizontally aligned with one another. In the illustratedembodiment, the second transducer beam portion 1408 of the loadtransducer 1400 comprises a strain gage 1432 disposed on a side surfacethereof that is sensitive to a second shear force component (i.e., aF_(X) strain gage) and substantially centered on the aperture 1416. Thesecond transducer beam portion 1408 also comprises a strain gage 1434disposed on a top surface thereof that is sensitive to a vertical forcecomponent (i.e., a F_(Z) strain gage) and substantially centered on theaperture 1418. In addition, the second transducer beam portion 1408 alsocomprises a set of strain gages 1436 a, 1436 b that are sensitive to athird moment component (i.e., a M_(X) strain gages). The strain gages1436 a, 1436 b are disposed on opposed top and bottom surfaces of thesecond transducer beam portion 1408, and are substantially verticallyaligned with one another. Also, in the illustrative embodiment, thethird transducer beam portion 1410 of the load transducer 1400 comprisesa strain gage 1430 disposed on a side surface thereof that is sensitiveto the first shear force component (i.e., a F_(Y) strain gage) andsubstantially centered on the aperture 1420. The third transducer beamportion 1410 also comprises a first set of strain gages 1438 a, 1438 bthat are sensitive to a first moment component (i.e., a M_(Y) straingages). The strain gages 1438 a, 1438 b are disposed on opposed top andbottom surfaces of the third transducer beam portion 1410, and aresubstantially vertically aligned with one another. The third transducerbeam portion 1410 additionally comprises a second set of strain gages1440 a, 1440 b that are sensitive to a second moment component (i.e., aM_(Z) strain gages). The strain gages 1440 a, 1440 b are disposed onopposed side surfaces of the third transducer beam portion 1410, and aresubstantially horizontally aligned with one another. The fourthtransducer beam portion 1412 of the load transducer 1400 comprises astrain gage 1432 disposed on a side surface thereof that is sensitive toa second shear force component (i.e., a F_(X) strain gage) andsubstantially centered on the aperture 1422. The fourth transducer beamportion 1412 also comprises a strain gage 1434 disposed on a top surfacethereof that is sensitive to a vertical force component (i.e., a F_(Z)strain gage) and substantially centered on the aperture 1424. Inaddition, the fourth transducer beam portion 1412 also comprises a setof strain gages 1436 a, 1436 b that are sensitive to a third momentcomponent (i.e., a M_(X) strain gages). The strain gages 1436 a, 1436 bare disposed on opposed top and bottom surfaces of the fourth transducerbeam portion 1412, and are substantially vertically aligned with oneanother. In the illustrated embodiment, the first shear force componentis generally perpendicular to the second shear force component, and eachof the first and second shear force components are generallyperpendicular to the vertical force component.

In the illustrated embodiment, the strain gages 1430, 1432, 1434 aredisposed on respective outer surfaces of the transducer beam portions1406, 1408, 1410, 1412. The outer surfaces of the transducer beamportions 1406, 1408, 1410, 1412 on which the strain gages 1430, 1432,1434 are disposed are generally opposite to the inner surfaces of therespective apertures 1414, 1416, 1418, 1420, 1422, 1424.

As shown in FIGS. 51-54 , the force component strain gages of theillustrated load cells are mounted on the top and outer side surfaces ofthe transducer beam portions 1406, 1408, 1410, 1412 of the loadtransducer 1400. Alternatively, the strain gages 1430, 1432 can bemounted to the inner side surfaces of the respective first and secondtransducer beam portions 1406, 1408, rather than to the outer sidesurfaces of the respective first and second transducer beam portions1406, 1408 as illustrated in FIGS. 51 and 54 . Similarly, the straingages 1430, 1432 can be mounted to the inner side surfaces of therespective third and fourth transducer beam portions 1410, 1412, ratherthan to the outer side surfaces of the respective third and fourthtransducer beam portions 1410, 1412 as illustrated in FIGS. 51 and 54 .In addition, the strain gages 1434 can be mounted to the bottom surfacesof the second and fourth transducer beam portions 1408, 1412, ratherthan to the top of the transducer beam portions 1408, 1412 asillustrated in FIGS. 51 and 54 . In general, the strain gages 1430,1432, 1434 are mounted to surfaces generally normal to the direction ofapplied vertical and/or shear forces (i.e., F_(X), F_(Y), F_(Z)). It isalso noted that alternatively, strain gages 1430 can be mounted at bothopposed side surfaces of first and third transducer beam portions 1406,1410 and/or strain gages 1432 can be mounted at both opposed sidesurfaces of the second and fourth transducer beam portions 1408, 1412.Similarly, strain gages 1434 can be mounted at both the top surface andthe bottom surface of the second and fourth transducer beam portions1408, 1412. These strain gages 1430, 1432, 1434 measure force either bybending moment or difference of bending moments at two cross sections.As force is applied to the central body portion 1402 of the loadtransducer 1400, the transducer beam portions bend. This bending eitherstretches or compresses the strain gages 1430, 1432, 1434, which in turnchanges the resistance of the electrical current passing therethrough.The amount of change in the electrical voltage or current isproportional to the magnitude of the applied force, as applied to thecentral body portion 1402 of the load transducer 1400.

In the illustrated embodiment, each of the strain gages 1430, 1432, 1434comprises a full-bridge strain gage configuration (i.e., four (4) activestrain gage elements wired in a Wheatstone bridge configuration), whileeach of the strain gages 1436 a, 1436 b, 1438 a, 1438 b, 1440 a, and1440 b comprises a half-bridge strain gage configuration (i.e., two (2)active strain gage elements). Also, in the illustrative embodiment, thepair of strain gages 1436 a, 1436 b are wired together in one Wheatstonebridge configuration (i.e., with a total of four (4) active strain gageelements), the pair of strain gages 1438 a, 1438 b are wired together inanother Wheatstone bridge configuration (i.e., with a total of four (4)active strain gage elements), and the pair of strain gages 1440 a, 1440b are wired together in yet another Wheatstone bridge configuration(i.e., with a total of four (4) active strain gage elements).

Turning again to FIGS. 51 and 54 of the illustrated embodiment, it canbe seen that the central body portion 1402 of the load transducer 1400comprises a plurality of mounting apertures 1442 (e.g., four apertures1442 arranged in 2×2 array) disposed therethrough for accommodatingfasteners (e.g., screws) that attach the load transducer 1400 to a firstobject, such as a plate component of a force plate or force measurementassembly (e.g., plate component 1152 in FIGS. 42 and 43 ). Also, asdepicted in FIGS. 51 and 54 , the second and fourth transducer beamportions 1408, 1412 of the load transducer 1400 each comprise a mountingaperture 1444 (e.g., a single aperture 1444) disposed therethrough nearthe respective free ends 1408 a, 1412 a for accommodating a fastener(e.g., a screw) that attaches the load transducer 1400 to a secondobject, such as a mounting foot of a force plate or force measurementassembly. The load applied to the load transducer 1400 is conveyedthrough the plurality of beam portions 1406, 1408, 1410, 1412 of theload transducer 1400 from the first object (e.g., the plate component1152 in FIGS. 42 and 43 ) to the second object (e.g., the mounting footof the force measurement assembly).

In the illustrative embodiment of FIGS. 51-54 , it can be seen that thecentral body portion 1402 of the load transducer 1400 comprises no otherapertures besides the mounting apertures 1442. That is, the central bodyportion 1402 is completely solid, except for the mounting apertures1442. Advantageously, the solid central body portion 1402 of the loadtransducer 1400 is structurally robust enough to support the load beingapplied to the object to which the load transducer 1400 is mounted(e.g., a plate component of a force measurement assembly) withoutundergoing excessive deformation (i.e., without undergoing non-elasticdeformation).

Referring now to the drawings, FIGS. 55-60 illustrate a load transducer1510 according to a seventeenth exemplary embodiment of the presentinvention. As shown in these figures, in the illustrated embodiment, theload transducer 1510 is in the form of a pylon-type load cell. The loadtransducer 1510 generally includes a one-piece compact transducer frameportion having a central cylindrical body portion 1514 and a pair offlanges 1512, 1516 disposed at opposite longitudinal ends of the centralcylindrical body portion 1514. In particular, the load transducer 1510includes a bottom flange 1512 disposed at the lower longitudinal end ofthe cylindrical body portion 1514, and a top flange 1516 disposed at theupper longitudinal end of the cylindrical body portion 1514. As bestillustrated in the perspective view of FIG. 55 and the sectional view ofFIG. 60 , the bottom flange 1512 comprises a plurality ofcircumferentially spaced-apart mounting apertures 1518 disposedtherethrough (e.g., eight (8) mounting apertures 1518 disposedtherethrough). Each of the mounting apertures 1518 is configured toreceive a respective fastener (e.g., a threaded screw or bolt) forsecuring the load transducer 1510 to an object (e.g., a bottom mountingplate). Similarly, as shown in FIG. 55 and top view of FIG. 59 , the topflange 1516 also comprises a plurality of circumferentially spaced-apartmounting apertures 1526 disposed therethrough (e.g., eight (8) mountingapertures 1526 disposed therethrough). Each of the mounting apertures1526 is configured to receive a respective fastener (e.g., a threadedscrew or bolt) for securing the load transducer 1510 to an object (e.g.,a top plate member).

With reference to FIGS. 55, 59, and 60 , it can be seen that, in theillustrative embodiment, the frame portion of the load transducer 1510includes a central aperture 1528 disposed therethrough in a longitudinaldirection of the load transducer 1510. As such, the central cylindricalbody portion 1514 of the load transducer 1510 is in the form of atubular member that undergoes elastic deformation when a load is appliedto the load transducer 1510. Advantageously, adding the central aperture1528 through the load transducer 1510 increases the sensitivity of theload transducer 1510.

In the illustrated embodiment, the frame portion of the load transducer1510 is milled as one solid and continuous piece of a single material.That is, the frame portion of the load transducer 1510 is of unitary orone-piece construction with the central cylindrical body portion 1514and the flanges 1512, 1516 integrally formed together. The frame portionof the load transducer 1510 is preferably machined in one piece fromaluminum, titanium, steel, or any other suitable material that meetsstrength and weight requirements. Alternatively, the central cylindricalbody portion 1514 of the load transducer 1510 may be formed separatelyfrom the flanges 1512, 1516, and then attached or joined to the flanges1512, 1516 in any suitable manner (e.g., by welding, etc.).

Referring collectively to FIGS. 55 and 60 , it can be seen that aplurality of deformation sensing elements (e.g., strain gages 1520,1522, 1524) are disposed on the outer periphery of the centralcylindrical body portion 1514 of the load transducer 1510. Inparticular, in the illustrative embodiment, each of a first pair ofstrain gages 1520 (see FIG. 60 ) is sensitive to a first force component(i.e., the x-component of the force, F_(X)) of the load and outputs oneor more first output signals representative of the first force component(F_(X)). As best shown in the sectional view of FIG. 60 , a first one ofthe strain gages 1520 is disposed opposite to a second one of the straingages 1520 across the longitudinal axis of the load transducer 1510. Inother words, the strain gages 1520 are spaced apart from one anotherabout the outer periphery of the central cylindrical body portion 1514by approximately 180 degrees.

With reference again to FIG. 60 , in the illustrative embodiment, eachof a second pair of strain gages 1522 (see FIG. 60 ) is sensitive to atorsional moment component (i.e., the z-component of the moment, M_(Z))of the load and outputs one or more second output signals representativeof the torsional moment component (M_(Z)). As best shown in thesectional view of FIG. 60 , like the strain gages 1520 described above,a first one of the strain gages 1522 is disposed opposite to a secondone of the strain gages 1522 across the longitudinal axis of the loadtransducer 1510. In other words, the strain gages 1522 are spaced apartfrom one another about the outer periphery of the central cylindricalbody portion 1514 by approximately 180 degrees.

Turning again to FIG. 60 , in the illustrative embodiment, each of athird pair of strain gages 1524 (see FIG. 60 ) is sensitive to a secondforce component (i.e., the y-component of the force, F_(Y)) of the loadand outputs one or more third output signals representative of thesecond force component (F_(Y)). As best shown in the sectional view ofFIG. 60 , like the strain gages 1520 and 1522 described above, a firstone of the strain gages 1524 is disposed opposite to a second one of thestrain gages 1524 across the longitudinal axis of the load transducer1510. In other words, the strain gages 1524 are spaced apart from oneanother about the outer periphery of the central cylindrical bodyportion 1514 by approximately 180 degrees.

In the illustrated embodiment, each of the strain gages 1520, 1522, 1524comprise a half bridge (e.g., a half Wheatstone bridge). Although, inother embodiments, the strain gages 1520, 1522, 1524 may comprise a fullbridge (e.g., a full Wheatstone bridge). Also, in the illustratedembodiment, each of the strain gages 1520, 1522, 1524 may produce aseparate output signal (e.g., output voltage) such that the loadtransducer 1510 produces a total of six (6) total output signals (e.g.,output voltages). Although, in other embodiments, the paired straingages 1520, 1522, 1524 may be wired together such that the loadtransducer 1510 only produces a total of three (3) output signals (e.g.,output voltages).

FIGS. 61-66 illustrate a load transducer 1510′ according to aneighteenth exemplary embodiment of the present invention. As shown inthese figures, similar to the seventeenth illustrative embodiment, theload transducer 1510′ is in the form of a pylon-type load cell. As such,the load transducer 1510′ is similar in many respects to the loadtransducer 1510 of the seventeenth embodiment described above. However,unlike the aforedescribed load transducer 1510, the load transducer1510′ has an elongated central cylindrical body portion 1514′ withredundant sets of deformation sensing elements (e.g., strain gages 1530,1532, 1534) disposed above the primary sets of deformation sensingelements (e.g., strain gages 1520, 1522, 1524). Advantageously,providing the redundant sets of deformation sensing elements (e.g.,strain gages 1530, 1532, 1534) allow the load transducer 1510′ tofunction normally even if one of the strain gages were to fail. That is,the strain gages 1530, 1532, 1534 allow for redundant measurement of theforce components and torsional component in critical applications (e.g.,when the load transducer 1510′ is being used to control an importantindustrial process, etc.). Thus, advantageously, the redundant sets ofdeformation sensing elements (e.g., strain gages 1530, 1532, 1534) allowthe load transducer 1510′ to produce the same output when one of theprimary deformation sensing elements (e.g., strain gages 1520, 1522,1524) experiences a failure.

Referring collectively to FIGS. 61 and 66 , it can be seen thatredundant sets of deformation sensing elements (e.g., strain gages 1530,1532, 1534) are disposed on the outer periphery of the centralcylindrical body portion 1514′ of the load transducer 1510′ above theprimary sets of deformation sensing elements (e.g., strain gages 1520,1522, 1524). Similar to the strain gages 1520 described above, in theillustrative embodiment, each of a first pair of redundant strain gages1530 (see FIG. 61 ) is sensitive to the first force component (i.e., thex-component of the force, F_(X)) of the load, and outputs one or morefirst output signals representative of the first force component(F_(X)). As best shown in the sectional view of FIG. 66 , a first one ofthe strain gages 1530 is disposed opposite to a second one of the straingages 1530 across the longitudinal axis of the load transducer 1510′. Inother words, the strain gages 1530 are spaced apart from one anotherabout the outer periphery of the central cylindrical body portion 1514of the load transducer 1510′ by approximately 180 degrees.

With reference again to FIG. 66 , similar to the strain gages 1522described above, in the illustrative embodiment, each of a second pairof redundant strain gages 1532 (see FIG. 61 ) is sensitive to thetorsional moment component (i.e., the z-component of the moment, M_(Z))of the load and outputs one or more second output signals representativeof the torsional moment component (M_(Z)). As best shown in thesectional view of FIG. 66 , like the strain gages 1522 described above,a first one of the redundant strain gages 1532 is disposed opposite to asecond one of the strain gages 1532 across the longitudinal axis of theload transducer 1510′. In other words, the strain gages 1532 are spacedapart from one another about the outer periphery of the centralcylindrical body portion 1514′ by approximately 180 degrees.

Turning again to FIG. 66 , in the illustrative embodiment, each of athird pair of redundant strain gages 1534 (see FIG. 61 ) is sensitive tothe second force component (i.e., the y-component of the force, F_(Y))of the load, and outputs one or more third output signals representativeof the second force component (F_(Y)). As best shown in the sectionalview of FIG. 66 , like the strain gages 1530 and 1532 described above, afirst one of the redundant strain gages 1534 is disposed opposite to asecond one of the strain gages 1534 across the longitudinal axis of theload transducer 1510′. In other words, the strain gages 1534 are spacedapart from one another about the outer periphery of the centralcylindrical body portion 1514′ by approximately 180 degrees.

Because the other features of the load transducer 1510′ have alreadybeen explained above in conjunction with the load transducer 1510, it isnot necessary to reiterate these features with respect to the loadtransducer 1510′. That is, the features that are common to both suchembodiments need not be repeated in conjunction with the description ofthe embodiment in FIGS. 61-66 .

In the illustrated embodiments, each of the strain gages 1520, 1522,1524, 1530, 1532, 1534 comprise a half bridge (e.g., a half Wheatstonebridge). Although, in other embodiments, the strain gages 1520, 1522,1524, 1530, 1532, 1534 may comprise a full bridge (e.g., a fullWheatstone bridge). Also, in the illustrated embodiments, each of thestrain gages 1520, 1522, 1524, 1530, 1532, 1534 may produce a separateoutput signal (e.g., output voltage) such that the load transducer 1510′produces a total of twelve (12) total output signals (e.g., outputvoltages). Although, in other embodiments, the paired strain gages 1520,1522, 1524 may be wired together, and the paired strain gages 1530,1532, 1534 also may be wired together, such that the load transducer1510′ only produces a total of six (6) output signals (e.g., outputvoltages).

FIG. 67 graphically illustrates the acquisition and processing of theload data carried out by the exemplary load transducer data processingsystem. Initially, as shown in FIG. 67 , a load L (e.g., forces and/ormoments) is applied to the load transducer 1510, 1510′. When theelectrical resistance of each strain gage 1520, 1522, 1524, 1530, 1532,1534 is altered by the application of the applied forces and/or moments,the change in the electrical resistance of the strain gages brings aboutconsequential changes in the output voltages of the strain gage bridgecircuits (e.g., a Wheatstone bridge circuits). Thus, in one embodiment,the three (3) pairs of strain gages 1520, 1522, 1524 output a total ofthree (3) analog output voltages (signals). In some embodiments, thethree (3) output voltages from the three (3) pairs of strain gages 1520,1522, 1524 are then transmitted to a preamplifier board (not shown) forpreconditioning. The preamplifier board is used to increase themagnitudes of the analog voltage signals, and preferably, to convert theanalog voltage signals into digital voltage signals as well. Afterwhich, the load transducer 1510, 1510′ transmits the output signalsS_(TO1)-S_(TO3) to a main signal amplifier/converter 1536. Depending onwhether the preamplifier board also includes an analog-to-digital (A/D)converter, the output signals S_(TO1)-S_(TO3) could be either in theform of analog signals or digital signals. The main signalamplifier/converter 1536 further magnifies the transducer output signalsS_(TO1)-S_(TO3), and if the signals S_(TO1)-S_(TO3) are of theanalog-type (for a case where the preamplifier board did not include ananalog-to-digital (A/D) converter), it may also convert the analogsignals to digital signals. Then, the signal amplifier/converter 1536transmits either the digital or analog signals S_(ACO1)-S_(ACO3) to thedata acquisition/data processing device 1538 (computer 1538) so that theforces and/or moments that are being applied to the load transducer1510, 1510′ can be transformed into output load values OL. The computeror data acquisition/data processing device 1538 may further comprise ananalog-to-digital (A/D) converter if the signals S_(ACO1)-S_(ACO3) arein the form of analog signals. In such a case, the analog-to-digitalconverter will convert the analog signals into digital signals forprocessing by the microprocessor of the computer 1538.

When the computer or data acquisition/data processing device 1538receives the voltage signals S_(ACO1)-S_(ACO3), it initially transformsthe signals into output forces and/or moments by multiplying the voltagesignals S_(ACO1)-S_(ACO3) by a stored calibration matrix. After which,the force components F_(X), F_(Y) and the torsional moment componentM_(Z) applied to the load transducer 1510, 1510′ are determined by thecomputer or data acquisition/data processing device 1538. The manner inwhich the stored calibration matrix is utilized to eliminate crosstalkbetween the output signals or channels will be explained in furtherdetail hereinafter.

Now, turning to FIG. 68 , it can be seen that the data acquisition/dataprocessing device 1538 (i.e., the computing device 1538) of the loadtransducer system 1550 comprises a microprocessor 1538 a for processingdata, memory 1538 b (e.g., random access memory or RAM) for storing dataduring the processing thereof, and data storage device(s) 1538 c, suchas one or more hard drives, compact disk drives, floppy disk drives,flash drives, or any combination thereof. As shown in FIG. 68 , one ormore load transducers 1510, 1510′ and a visual display device 1544 areoperatively coupled to the core components 1538 a, 1538 b, 1538 c of thedata acquisition/data processing device 1538 such that data is capableof being transferred between these devices 1510, 1510′, 1538, and 1544.Also, as illustrated in FIG. 68 , a plurality of data input devices1540, 1542 such as a keyboard 1540 and mouse 1542 are operativelycoupled to the core components 1538 a, 1538 b, 1538 c of the dataacquisition/data processing device 1538 so that a user is able to enterdata into the data acquisition/data processing device 1538. In someembodiments, the data acquisition/data processing device 1538 can be inthe form of a laptop computer, while in other embodiments, the dataacquisition/data processing device 1538 can be embodied as a desktopcomputer.

As will be described hereinafter, in the illustrative embodiment, thedata acquisition/data processing device 1538 is configured to utilizethe stored calibration matrix in order to substantially eliminatecrosstalk between the transducer output signals S_(TO1)-S_(TO3) so thatthe respective transducer output signals are generally representativeonly of a respective one of the force or moment components (F_(X),F_(Y), M_(Z)).

For example, initially referring to the signal flow diagram depicted inFIG. 69 , the load L (t) applied to the transducer causes thedeformation of the transducer strain gages. The response of thetransducer to such deformation is denoted by the operator

in FIG. 69 . The strain signals from the strain gages are digitized intotime-dependent raw load signals B(t). Inherently, the strain signals arealso a function of the applied load: B(t)≡B(L(t),t).

The transducer's operating conditions P(t) other than mechanical loads,such as temperatures, can have an effect on the transducer response

. They can also be collected and digitized into time-dependent auxiliarysignals A(t), subject to their own auxiliary response

_(P). In addition to temperature, operating conditions P(t) that canaffect the transducer response include the ambient pressure in theenvironment containing the load transducer, magnetic fields present inthe environment, and non-inertial conditions (i.e., accelerations otherthan gravitational acceleration).

When the transducer has a generally linear response to the applied load,and when the operating conditions P(t) are presumed to have a negligibleeffect on the transducer response, the calibrated load F(t) may bedetermined from the following equation:F(t)=C·B(t)  (1)

where:

F(t): calibrated load;

C: calibration function; and

B(t): raw load.

Thus, using equation (1) above, the raw loads are calibrated using thecalibration function C to obtain the calibrated load F. The calibrationfunction is the outcome of a transducer calibration process.

In general, crosstalk in the raw load B is the linear dependence of anyone component of the raw load on more than one component of the appliedload L. Given a transducer with a linear response

such that rank(

)≥l (or l_(n)≥l), there exists a linear transformation CB such thatCB≈L: it recovers and separates the individual components of the appliedload so that they become linearly independent. The linear independenceof the components of F is equivalent to lack of cross-talk.

For example, in one embodiment, a 2-axis sensor with two raw load signalcomponents and two calibrated load signal components is provided. Due tothe design of the transducer, each of the raw load signals is a linearcombination of both components of the load that are being sensed, asdescribed by the following two equations:B ₁(t)=100F ₁(t)+100F ₂(t)  (2)B ₂(t)=−100F ₁(t)+100F ₂(t)  (3)The response

of this transducer is linear and given by the following matrix:

$\begin{matrix}{\mathcal{D} = \begin{bmatrix}{100} & {100} \\{{- 1}00} & {100}\end{bmatrix}} & (4)\end{matrix}$Because both B₁ and B₂ carry a measure of F₁ and F₂, there is crosstalk.The following matrix separates these signals:

$\begin{matrix}{C = {\mathcal{D}^{- 1} = \begin{bmatrix}{{0.0}05} & {{- {0.0}}05} \\{{0.0}05} & {{0.0}05}\end{bmatrix}}} & (5)\end{matrix}$Generally, for non-rectangular C and

, it holds that

·C≈I, where I is an identity matrix. In other words,

is a pseudoinverse of C.

Also, in the illustrative embodiment, data acquisition/data processingdevice 1538 is additionally configured to determine one or moredeformation compensation parameters for the load transducer system 1550and to correct the one or more respective output forces or moments usingthe one or more deformation compensation parameters. For example, withcombined reference to FIGS. 55 and 60 , suppose that it is desired todetermine the x-component of the force (F_(X)) using the load transducer1510. As explained above, the pair of strain gages 1520 is sensitive tothe x-component of the force (F_(X)). However, because the transducerframe of the load transducer 1510 is not perfectly symmetrical (e.g.,due to machining imperfections) and the strain gages 1520, 1522, 1524are not perfectly positioned on the transducer frame of the loadtransducer 1510, the strain gages 1522, 1524, which are not designed tobe sensitive to the x-component of the force (F_(X)), will output anon-zero signal when only a force in the x-direction is applied to thepylon-type load transducer 1510. The data acquisition/data processingdevice 1538 may correct the load transducer output by using thefollowing equation:F _(x)=(S _(x) ·A)+(S _(y) ·B)+(S _(T) ·C)  (6)where:

-   -   F_(x): x-component of the force, which is the desired measured        quantity;    -   S_(x): signal from strain gages 1520 that are sensitive to the        x-component of the force;    -   A: calibration coefficient for the x-component of the force;    -   S_(y): signal from strain gages 1524 that are sensitive to the        y-component of the force;    -   B: calibration coefficient for the y-component of the force;    -   S_(T): signal from strain gages 1522 that are sensitive to the        torsional moment component (M_(Z)); and    -   C: calibration coefficient for the torsional moment component        (M_(Z)).        As such, the data acquisition/data processing device 1538 uses        the deformation output signals S_(Y), S_(T) from the strain        gages 1522, 1524 in order to correct the x-component of the        force. That is, the terms (S_(y)·B) and (S_(T)·C) in        equation (6) are deformation compensation parameters that are        used to correct the x-component of the force so that the        imperfections in the machining of the frame portion of the load        transducer 1510 and the imperfect placement of the strain gages        may compensated for in the determination of the output force        (F_(X)), thereby resulting in a more accurate determination of        the output force (F_(X)).

In addition, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 is further configured to determine one or moretemperature compensation parameters for the load transducer system 1550,and to correct the transducer output signals S_(TO1)-S_(TO3) using theone or more temperature compensation parameters. The dataacquisition/data processing device 1538 is further configured todetermine the respective force or moment components (F_(X), F_(Y),M_(Z)) from the respective transducer output signals S_(TO1)-S_(TO3).

In one or more embodiments, the load transducer 1510 further comprisesone or more temperature sensing elements 1546 disposed thereon (seeFIGS. 55, 56, and 58 ). For example, in some embodiments, the one ormore temperature sensing elements 1546 may comprise one or morethermistors. In other embodiments, one or more of the strain gages 1520,1522, 1524 may be used as the temperature sensing elements so thatadditional temperature sensing elements are not required. In these oneor more embodiments, the one or more temperature sensing elements areconfigured to output one or more temperature output signals indicativeof a temperature of at least a portion of the load transducer 1510. Theone or more temperature sensing elements are operatively coupled to thedata acquisition/data processing device 1538. The data acquisition/dataprocessing device 1538 is configured to receive the one or morerespective temperature output signals from the one or more temperaturesensing elements, and to determine the one or more temperaturecompensation parameters based upon the one or more respectivetemperature output signals for correcting the force and/or momentcomponents (F_(X), F_(Y), M_(Z)).

In one or more alternative embodiments, rather than using temperaturesensing elements to determine the temperature compensation parameters,the data processing device is configured to determine the one or moretemperature compensation parameters based upon the one or moreexcitation current values associated with the one or more deformationsensing elements (e.g., strain gages 1520, 1522, 1524) of the loadtransducer 1510. In these one or more alternative embodiments, the oneor more excitation current values may be determined by measuring theexcitation current of the strain gage bridge circuits of the loadtransducer 1510 (e.g., the current flowing through a particular one ofthe strain gages). The resistance of the strain gages 1520, 1522, 1524changes in accordance with the ambient temperature of the environment inwhich the load transducer 1510 is disposed.

In the illustrative embodiment, the data acquisition/data processingdevice 1538 may utilize the one or more temperature compensationparameters (as determined from either one or more temperature sensingelements or the one or more excitation current values) to correct fortemperature-induced effects on the zero drift of the load transducer1510. Also, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 may utilize the one or more temperaturecompensation parameters to correct for temperature-induced effects onthe sensitivity of the load transducer 1510.

Further, in the illustrative embodiment, the data acquisition/dataprocessing device 1538 may be additionally configured to determine aposition of the applied load using the load transducer system 1550, andto correct the one or more output forces or moments based upon theposition of the applied load. In particular, as will be explainedhereinafter, in one or more embodiments, the data acquisition/dataprocessing device 1538 is configured to correct the one or more outputforces or moments of the load transducer system 1550 by utilizing amathematical relationship (e.g., a polynomial function) that is basedupon the position of the applied load.

In one or more embodiments, to correct for errors correlated to thepoint of application of the load, a nonlinear calibration function isutilized. There is a general form of such calibration function that iseasy to compute and is a good representation of the nonlinearitiestypical of transducers. First, the linear calibration function based onthe calibration matrix

, as usually used for calibration of load sensors, is

≡

B.  (7)The generalized form of the calibration function uses a generalizationof the calibration matrix to a multivariate polynomial matrix

(B) of degree N on the elements of the raw load vector B:

≡

(B)B,  (8)where each i, j-th element of the polynomial matrix

(B) is a general multivariate polynomial of degree N in each element ofB. Given a b-dimensional B, and c_(i,j,1), . . . ,

$c_{i,j,{(\begin{matrix}{b + N} \\b\end{matrix})}}$are its coefficients, and the multivariate polynomial matrix's elementsare of the following degree-lexicographically ordered form, where thelexicographic order is on the elements of B:

$\begin{matrix}{{\mathbb{C}}_{i,j} = {c_{i,j,1} + {c_{i,j,2}B_{1}} + \ldots + {c_{i,j,{({b + 2})}}B_{1}^{2}} + \ldots + {c_{i,j,{({{Nb} + 1})}}B_{b}^{N}} + \ldots + {c_{i,j,{(\begin{matrix}{b + N} \\b\end{matrix})}}\left( {B_{1}^{N}\mspace{14mu}\ldots\mspace{14mu} B_{b}^{N}} \right)}}} & (9)\end{matrix}$There are

$l \cdot c \cdot \begin{pmatrix}{b + N} \\b\end{pmatrix}$polynomial coefficients in the polynomial matrix

(B), where l is the dimension of the calibrated load vector F.

In practice, it is often sufficient to use a specialized form ofmultivariate polynomials, with some classes of the monomials having zerocoefficients. For example, a multivariate polynomial might include allsingle-variable terms up to N-th order, i.e. terms of the form B_(i)^(n), where n≤N, then all mixed terms of up to q variables up to M-thorder, i.e. of the form B_(i) ₁ ^(m) ¹ · . . . ·B_(i) _(q) ^(m) ^(q) ,where m_(q) and i_(q) are the exponents and component indices in theq-th element of the term.

The multivariate polynomial calibration matrix elements can determinedduring the calibration process, by solving a linear system of equations

(B_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l). Theunknowns are the values of coefficients c_(i,j,k), where i covers theindices of the applied load, j covers the indices of the raw load, and kcovers the indices of the multivariate polynomial of the chosendimension N. In practical applications, where the number of polynomialcoefficients to be determined is much smaller than the number of appliedcalibration points, the resulting coefficient vectors building up C arelinear combinations of basis vectors, and further constraints are usedto select a single scalar for each coefficient. Such constraint can bee.g. a minimal-norm criterion for the vector of coefficients of

.

In one or more embodiments, to correct for errors correlated to theoperating conditions P, a nonlinear calibration function is utilized.The auxiliary signal A, representing the operating conditions, caninclude elements that are measures of any of the following: (i)temperature at one or more locations within the load sensor, (ii)resistance of one or more strain gage bridges, measured across theirexcitation voltage inputs, (iii) resistance of one or more strain gagehalf-bridges, either individual or forming a full bridge, measuredacross their excitation voltage inputs, (iv) atmospheric pressure, (v)components of magnetic field measured using a Hall sensor at one or morelocations within the load sensor, and (vi) components of magnetic fieldmeasured using sense coils and represented by the voltages induced inthese coils.

The generalized form of the calibration function uses a generalizationof the calibration matrix to a multivariate polynomial matrix

(A) of degree N on the elements of auxiliary signal vector A, used tocalibrate the raw load vector B:

≡

(A)B,  (10)where each i, j-th element of the polynomial matrix

(A) is a general multivariate polynomial of degree N in each element ofA. Given an a-dimensional A, and its coefficients c_(i,j,1), . . . ,c_(i,j,() _(a+N) _(a) ₎, the multivariate polynomial matrix's elementsare of the following degree-lexicographically ordered form, where thelexicographic order is on the elements of A:

$\begin{matrix}{{\mathbb{C}}_{i,j} = {c_{i,j,1} + {c_{i,j,2}A_{1}} + \ldots + {c_{i,j,{({a + 2})}}A_{1}^{2}} + \ldots + {c_{i,j,{({{Na} + 1})}}A_{a}^{N}} + \ldots + {{c_{i,j,{(\begin{matrix}{a + N} \\b\end{matrix})}}\left( {A_{1}^{N}\mspace{14mu}\ldots\mspace{14mu} A_{a}^{N}} \right)}.}}} & (11)\end{matrix}$There are

$l \cdot c \cdot \begin{pmatrix}{a + N} \\a\end{pmatrix}$polynomial coefficients in the polynomial matrix

(A), where l is the dimension of the calibrated load vector F. Themultivariate polynomial matrix of a sufficient degree corrects for bothzero drift and the sensitivity of the transducer.

In practice, it is often sufficient to use a specialized form ofmultivariate polynomials, with some classes of the monomials having zerocoefficients. For example, a multivariate polynomial might include allsingle-variable terms up to N-th order, i.e. terms of the form A_(i)^(n), where n≤N, then all mixed terms of up to q variables up to M-thorder, i.e. of the form

A_(i₁)^(m₁) ⋅ … ⋅ A_(i_(q))^(m_(q)),where m_(q) and i_(q) are the exponents and component indices in theq-th element of the term.

The multivariate polynomial calibration matrix elements can bedetermined during the calibration process, by solving a linear system ofequations

(A_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l), undersome conditions that resulted in A_(l). The unknowns are the values ofcoefficients c_(i,j,k), where i covers the indices of the applied load,j covers the indices of the raw load, and k covers the indices of themultivariate polynomial of the chosen dimension N. In practicalapplications, where the number of polynomial coefficients to bedetermined is much smaller than the number of applied calibrationpoints, the resulting coefficient vectors building up

are linear combinations of basis vectors, and further constraints areused to select a single scalar for each coefficient. Such constraint canbe e.g. a minimal-norm criterion for the vector of coefficients of

.

In one or more further embodiments, the load accuracy and operatingconditions corrections may be applied with their multivariate polynomialmatrices separated, first applying the load accuracy correctioncalibration, and then the operating conditions correction:

≡

₁(A)

₂(B)B.  (12)Alternatively, the load accuracy and operating condition corrections canbe expressed using a single multivariate polynomial matrix on thecoefficients of both the auxiliary and raw load vectors:

≡

(A,B)B.  (13)

The multivariate polynomial calibration matrix

's elements can be determined during the calibration process, by solvinga linear system of equations

((A,B)_(l))B_(l)=L_(l) for each l-th applied calibration load L_(l),under some conditions where (A, B)_(l) is the concatenation of the rawload and auxiliary signal vectors. The unknowns are the values ofcoefficients c_(ij,k), where i covers the indices of the applied load, jcovers the indices of the concatenation of the raw load and auxiliarysignal vectors, and k covers the indices of the multivariate polynomialof the chosen dimension N. In practical applications, where the numberof polynomial coefficients to be determined is much smaller than thenumber of applied calibration points, the resulting coefficient vectorsbuilding up

are linear combinations of basis vectors, and further constraints areused to select a single scalar for each coefficient. Such constraint canbe e.g. a minimal-norm criterion for the vector of coefficients of

.

One or more further illustrative embodiments will be described withreference to FIGS. 70-74 . In these one or more further illustrativeembodiments, a force measurement system, which may be in the form of theforce measurement system depicted in FIG. 42 with force measurementassembly 1150 and data acquisition/data processing device 1174, isconfigured to more accurately determine the forces and/or moments of aload applied to a particular region of the force measurement assembly.Initially, referring to FIG. 70 , an exemplary top plate component 1610of the force measurement system is illustrated with coordinatemeasurement axes 1618, 1620, 1622 and a plurality of calibration points1624, 1628, 1632 depicted on the top plate component 1610. In theillustrative embodiment, the top plate component 1610 of the forcemeasurement system depicted in FIG. 70 may have six outputs (F_(x),F_(y), F_(z), M_(x), M_(y), M_(z)) and the illustrated XYZ coordinatesystem. As shown in FIG. 70 , the X and Y axes 1618, 1620 are coplanarto the top surface 1612 and perpendicular to each other. Also, as shownin the illustrative embodiment of FIG. 70 , the Z axis 1622 points downinto the top plate component 1610. The origin is located at the centerof the top surface 1612 of the top plate component 1610 of the forcemeasurement assembly.

In the illustrative embodiment, the force measurement assembly with topplate component 1610 is provided with two or more or more load-sensingcells (e.g., the two load transducers 1100 in FIG. 42 ) disposedunderneath the top plate component 1610. As will be described in detailhereinafter, the load-sensing cells or load transducers of the forcemeasurement assembly are calibrated by applying known loads at knownlocations so as to convert the raw signal output into a calibratedoutput. For a six-component force measurement assembly with the topplate component 1610 depicted in FIG. 70 , at least six calibrationpoints are needed to solve for all unknown variables using aleast-squares fit. This collection of calibrations points is called acalibration matrix. This calibration matrix is multiplied by the rawsignal output to provide the six calibrated outputs of the forcemeasurement assembly.

Now, with reference to the flowchart illustrated in FIG. 72 , anillustrative calibration procedure for the force measurement assemblywith the top plate component 1610 depicted in FIGS. 70 and 71 will bedescribed. The calibration process begins at step 1644, and then one ormore pluralities of points are selected on one or more surfaces of theforce measurement assembly for applying one or more known loads in step1646. In particular, referring again to FIG. 70 , a first plurality ofvertical force calibration points 1624 arranged in a grid pattern may beselected on the top surface 1612 of the top plate component 1610 (e.g.,5×19 array of grid points totaling 95 overall points on the top surface1612). A second plurality of first shear force calibration points 1628arranged in a linear pattern may be selected on the first side surface1614 of the top plate component 1610 (e.g., 19 shear points for theshear force in the x-direction). A third plurality of second shear forcecalibration points 1632 arranged in a linear pattern may be selected onthe second side surface 1616 of the top plate component 1610 (e.g., 5shear points for the shear force in the y-direction).

Turning again to FIG. 72 , after the calibration points are selected instep 1646, one or more known loads are applied at the pluralities ofpoints 1624, 1628, 1632 on the surfaces 1612, 1614, 1616 of the topplate component 1610 of the force measurement assembly in step 1648. Forexample, in the illustrative embodiment, one or more calibration weightswith known weights are applied at each of the points 1624, 1628, 1632 onthe surfaces 1612, 1614, 1616 of the top plate component 1610. Then, instep 1650, after each known load is applied, the raw load data for eachof the points 1624, 1628, 1632 on the surfaces 1612, 1614, 1616 of thetop plate component 1610 of the force measurement assembly is storedusing the data processing device (e.g., using the data acquisition/dataprocessing device 1174 in FIG. 42 ).

Next, in step 1652, a global calibration matrix for the forcemeasurement assembly is generated, by using the data processing device1174, using the stored raw load data for the pluralities of points 1624,1628, 1632 on the surfaces 1612, 1614, 1616 of the top plate component1610 of the force measurement assembly. As shown by equation (14) below,in general, the calibration matrix is multiplied by the raw signaloutput to provide the six calibrated outputs of the force measurementassembly.

$\begin{matrix}{\begin{bmatrix}F_{x} \\F_{y} \\F_{z} \\M_{x} \\M_{y} \\M_{z}\end{bmatrix} = {\lbrack C\rbrack\begin{bmatrix}S_{F_{x}} \\S_{F_{y}} \\S_{F_{z}} \\S_{M_{x}} \\S_{M_{y}} \\S_{M_{z}}\end{bmatrix}}} & (14)\end{matrix}$

where:

F_(x), F_(y), F_(z): forces along each axis;

M_(x), M_(y), M_(z): moments about each axis;

C: calibration matrix; and

S_(F) _(x) , S_(F) _(y) , S_(F) _(z) , S_(M) _(x) , S_(M) _(y) , S_(M)_(z) : raw output signals from each channel.

Because all values except for the C matrix are known, equation (14) canbe solved as shown below:

$\begin{matrix}{\lbrack C\rbrack = {{\begin{bmatrix}F_{x} \\F_{y} \\F_{z} \\M_{x} \\M_{y} \\M_{z}\end{bmatrix}\begin{bmatrix}S_{F_{x}} \\S_{F_{y}} \\S_{F_{z}} \\S_{M_{x}} \\S_{M_{y}} \\S_{M_{z}}\end{bmatrix}}^{T}\left\{ {\begin{bmatrix}S_{F_{x}} \\S_{F_{y}} \\S_{F_{z}} \\S_{M_{x}} \\S_{M_{y}} \\S_{M_{z}}\end{bmatrix}\begin{bmatrix}S_{F_{x}} \\S_{F_{y}} \\S_{F_{z}} \\S_{M_{x}} \\S_{M_{y}} \\S_{M_{z}}\end{bmatrix}}^{T} \right\}^{- 1}}} & (15)\end{matrix}$By simplifying equation (15), the following equation is obtained:[C]=[F][S]^(T){[S][S]^(T)}⁻¹  (16)

where:

C: calibration matrix;

F: known loads;

S: raw output signals;

[S]^(T): transpose of the S matrix; and

{[S][S]^(T)}⁻¹: inverse of the raw signals post-multiplied by itstranspose.

In order to achieve an error of less than 1% in the computation of theglobal calibration matrix, a minimum of fifteen (15) calibration pointsneed to be taken on the top plate component 1610 of FIG. 70 for thesix-component force measurement assembly. For example, referring againto FIG. 70 , the nine points 1626 (points 1-9 in FIG. 70 ) may be usedon the top surface 1612 of the top plate component 1610 to form a 3×3grid for the computation of the global calibration matrix, rather all 95points described above. In addition, for the shear forces, two 1×3 gridsof points 1630, 1634 (points 10-15 in FIG. 70 ) may be used on the sides1614, 1616 of the top plate component 1610 for the computation of theglobal calibration matrix, rather all 24 side points described above.Then, as described above, a known load is applied at each point 1626,1630, 1634 and the load value, point of application and vector ofapplication are stored. When data has been stored for all 15 points,there will be a 15×6 matrix of known loads, F, and an 8×15 matrix of rawsignal output, S. Using the F and S matrices and equation (16) above, a6×8 global calibration matrix, C_(G), is then generated by the dataprocessing device 1174. After the global calibration matrix, C_(G), hasbeen generated by the data processing device 1174 in step 1652, theglobal calibration matrix is stored in non-volatile memory (e.g., in thememory 1174 b or on the data storage device(s) 1174 c of the dataprocessing device 1174) in step 1654 of the calibration process. Theglobal calibration matrix, C_(G), is used to convert the raw signaloutput from the force measurement assembly into calibrated data anddetermine the values of unknown loads.

Referring again to the illustrative embodiment of FIG. 72 , after theglobal calibration matrix C_(G) has been generated by the dataprocessing device 1174, in step 1656, the data processing device 1174further generates local calibration matrices for a plurality ofdifferent load regions 1636 on the surface 1612 of the top platecomponent 1610 of the force measurement assembly in FIG. 70 to furtherreduce measurement errors when unknown forces and moments are determinedusing the force measurement assembly. In the illustrative embodiment, alocal calibration matrix C_(Li) may be determined for each of theeighteen (18) load regions 1636 in FIG. 70 (i.e., local calibrationmatrices, C_(Li), are determined, where i=1: 18 in the illustrativeembodiment). When the local calibration matrices C_(Li) are determinedduring the calibration process of the force measurement assembly as instep 1656 of FIG. 72 , the area on the top and sides of the top platecomponent 1610 may be divided into 18 subsets (an example of a subset isshown using larger, hatched points in FIG. 71 ). As shown in FIG. 71 ,the example subset includes nine (9) calibration points 1638 disposed onthe top surface 1612 of the top plate component 1610, three (3)calibration points 1640 disposed on the first side surface 1614 of thetop plate component 1610, and three (3) calibration points 1642 disposedon the second side surface 1616 of the top plate component 1610. Asshown in FIG. 71 , the three (3) calibration points 1640 disposed on thefirst side surface 1614 of the top plate component 1610 and the three(3) calibration points 1642 disposed on the second side surface 1616 ofthe top plate component 1610 are aligned with the nine (9) calibrationpoints 1638 disposed on the top surface 1612 of the top plate component1610. By applying known loads at each of the fifteen (15) pointscorresponding to each of the load regions 1636 in FIGS. 70 and 71 , alocal calibration matrix C_(Li) is computed for each of the load regions1636. Using the F and S matrices and equation (16) above, a 6×8 localcalibration matrix C_(Li) is then generated by the data processingdevice 1174 for each of the load regions 1636 in FIGS. 70 and 71 . Aftereach of the local calibration matrices C_(Li) have been generated by thedata processing device 1174 in 1656, the local calibration matricesC_(Li) are stored in non-volatile memory (e.g., in the memory 1174 b oron the data storage device(s) 1174 c of the data processing device 1174)in step 1658 of the calibration process, and then, the process isconcluded in step 1660. The local calibration matrices C_(Li) are usedto convert the raw signal output from the force measurement assemblyinto calibrated data and determine the values of unknown loads lying inthe specific load regions 1636 of the top plate component 1610.

Next, with reference to the flowchart illustrated in FIG. 73 , a firstillustrative load correction procedure for the force measurementassembly with the top plate component 1610 depicted in FIGS. 70 and 71will be described. In this first load correction procedure, precomputedlocal calibration matrices are used to correct the unknown load appliedto the top plate component 1610 of the force measurement assembly. Thefirst illustrative load correction process begins at step 1662, and thenan unknown load is applied on the surface of the force measurementassembly (e.g., on the top surface 1612 of the top plate component 1610of the force measurement assembly) in step 1664 of FIG. 73 . After theunknown load is applied in step 1664, the data processing device (e.g.,the data acquisition/data processing device 1174 in FIG. 42 )determines, in step 1666, a location of the applied load on the surfaceof the top plate component 1610 of the force measurement assembly usingthe stored global calibration matrix C_(G), which was determined in thecalibration process explained above. When the unknown load is applied tothe surface of the top plate component 1610, the global calibrationmatrix C_(G) determines the location of loading. Initially, the dataacquisition/data processing device 1174 utilizes the global calibrationmatrix C_(G) to determine the applied forces and moments(F_(x),F_(y),F_(z),M_(x),M_(y),M_(z)). Then, the data acquisition/dataprocessing device 1174 uses equations (17) and (18) below to determinethe center of pressure (COP) or point of application of the appliedload:x=−M _(y) /F _(z)  (17)y=−M _(x) /F _(z)  (18)

where:

-   -   x, y: coordinates of the point of application for the force        (i.e., center of pressure) on the top plate component 1610;    -   F_(z): z-component of the resultant force acting on the top        plate component 1610;    -   M_(x): x-component of the resultant moment acting on the top        plate component 1610; and    -   M_(y): y-component of the resultant moment acting on the top        plate component 1610.

Then, in the illustrative embodiment, once equations (17) and (18) areused to determine the location of force application, the applied load isassigned to one or more of the load regions 1636 on the surface of thetop plate component 1610 based upon the location of the applied load instep 1668 of FIG. 73 . In the illustrative embodiment, the dataprocessing device 1174 is configured to assign the applied load to oneor more of the plurality of load regions 1636 based upon the location ofthe applied load by using one or more mathematical inequalities. Inapplying the mathematical inequalities, an iterative process may beutilized by the data processing device 1174 in which it is determinedwhether the load coordinates x, y lie between a predetermined range of xand y values (e.g., initially determine −10<x<10 and 10<y<10). In theillustrative embodiment, the upper and lower limits of the mathematicalinequalities utilized by the data processing device 1174 may getprogressively smaller during the iterative process in order to determinethe load regions or regions 1636 in which the applied load is located.

After the applied load is assigned to one or more of the load regions1636 on the top surface 1612 of the top plate component 1610 of theforce measurement assembly, a corresponding local calibration matrixC_(Li) is selected by the data processing device 1174 to refine thecalibrated outputs. When the applied load lies within a single loadregion 1636 on the top surface 1612 of the top plate component 1610 ofthe force measurement assembly, the corresponding single localcalibration matrix C_(Li) is utilized by the data processing device1174. Although, in the illustrative embodiment, when multiple localcalibration matrices C_(Li) are equidistant from the location of forceapplication (e.g., when the x and y coordinates of the point ofapplication for the force lies on one of the boundaries 1637 between theload regions 1636 in FIGS. 70 and 71 ), the calibrated values from eachlocal calibration matrix C_(Li) are averaged before being output.

Referring again to FIG. 73 , after the local calibration matrix ormatrices C_(Li) corresponding to the load are selected, one or moreoutput forces or moments of the applied load are computed by the dataprocessing device 1174 using the selected local calibration matrix ormatrices for the one or more of the load regions 1636 on the surface offorce measurement assembly in step 1670. In particular, the one or moreoutput forces or moments of the applied load are computed using equation(14) above by the data processing device 1174, wherein the selectedlocal calibration matrix or averaged local calibration matrix (when thex and y coordinates of the point of application for the force lies onone of the boundaries 1637 between the load regions 1636) is used forthe calibration matrix C in equation (14). After the corrected outputforces and/or moments of the applied load are determined by the dataprocessing device 1174 in step 1670, the load correction processconcludes at step 1672 in FIG. 73 .

In one or more alternative embodiments, rather than determining acorrected applied load using a local calibration matrix, the correctedapplied load may be determined by applying a mathematical correctionfactor that is not in the form of a matrix. For example, once theposition of the applied load is determined using the global calibrationmatrix, a correction factor may be applied to the entries of the globalcalibration matrix based upon the position of the applied load. Inparticular, as one such example, a global calibration matrix and aresulting calibrated output may initially be determined (F_(x,g)=20.1lbf (89.41 N)). Then, the center of pressure (COP) location and thelocalized calibration data is used to determine a new value that is moreaccurate for that region of the force plate (F_(x,l)=20.2 lbf (89.85N)). After which, the local value for F_(Z) is divided by the globalvalue of F_(z) to get a “correction factor”, in this case CF_(Fx)=1.005,and then that value is stored as a “correction factor” for F_(z) in thatregion of the force plate. In equation form, the correction may berepresented as:

$\begin{matrix}{{CF} = \frac{F_{l}}{F_{g}}} & (19)\end{matrix}$

where:

-   -   CF: correction Factor;    -   F_(l): calibrated force output calculated by the local        calibration matrix; and    -   F_(g): Calibrated force output calculated by the global        calibration matrix.        Equation (19) may be expanded to show all the different        variables as follows:

$\begin{matrix}{{{{CF_{Fx}} = \frac{F_{x,l}}{F_{x,g}}},{{CF_{Fy}} = \frac{F_{y,l}}{F_{y,g}}},{{CF_{Fz}} = \frac{F_{z,l}}{F_{z,g}}}}{{{CF_{Mx}} = \frac{M_{x,l}}{M_{x,g}}},{{CF_{My}} = \frac{M_{y,l}}{M_{y,g}}},{{CF_{Mz}} = \frac{M_{z,l}}{M_{z,g}}}}} & (20)\end{matrix}$Advantageously, the calculation of the correction factor in the mannerabove simplifies the calculation of the calibrated output when the forceplate is in use.

Now, with reference to the flowchart illustrated in FIG. 74 , a secondillustrative load correction procedure for the force measurementassembly with the top plate component 1610 depicted in FIGS. 70 and 71will be described. In this second load correction procedure, the localcalibration matrix is computed during the load computational processusing the stored calibration data for a plurality of calibration points(i.e., the local calibration matrix is computed “on the fly” during theload computational process), rather than being precomputed. The secondillustrative load correction process begins at step 1674, and then anunknown load is applied on the surface of the force measurement assembly(e.g., on the top surface 1612 of the top plate component 1610 of theforce measurement assembly) in step 1676 of FIG. 74 . After the unknownload is applied in step 1676, the data processing device (e.g., the dataacquisition/data processing device 1174 in FIG. 42 ) determines, in step1678, a location of the applied load on the surface of the top platecomponent 1610 of the force measurement assembly using the stored globalcalibration matrix C_(G), which was determined in the calibrationprocess explained above. When the unknown load is applied to the surfaceof the top plate component 1610, the global calibration matrix C_(G)determines the location of loading. Initially, the data acquisition/dataprocessing device 1174 utilizes the global calibration matrix C_(G) todetermine the applied forces and moments (F_(x), F_(y), F_(z), M_(x),M_(y), M_(z)). Then, the data acquisition/data processing device 1174uses equations (17) and (18) above to determine the center of pressure(COP) or point of application of the applied load.

Then, in the illustrative embodiment, once equations (17) and (18) areused to determine the location of force application, the dataacquisition/data processing device 1174 references stored calibrationdata for a plurality of calibration points disposed proximate to thelocation of the applied load in step 1680. That is, in the illustrativeembodiment, after the global calibration matrix C_(G) specifies aninitial estimation of the location of force application, a subset ofdata is created quasi-instantaneously from the raw load data acquired instep 1650. In the illustrative embodiment, the subset of data createdfrom the raw load data is centered (as close as the data will allow)about the location of force application.

After creating the subset of data centered about the location of forceapplication from the raw load data in step 1680 (i.e., the storedcalibration data for the plurality of calibration points), the dataacquisition/data processing device 1174 generates a local calibrationmatrix C_(L) using the stored calibration data for the plurality ofcalibration points disposed proximate to the location of the appliedload (i.e., the data acquisition/data processing device 1174 generates alocal calibration matrix C_(L) “on the fly” customized for thatparticular force plate location) in step 1682. Referring again to FIG.74 , after the local calibration matrix C_(L) disposed proximate to thelocation of the applied load is determined, one or more output forces ormoments of the applied load are computed by the data processing device1174 using the local calibration matrix C_(L) determined in step 1682.In particular, the one or more output forces or moments of the appliedload are computed using equation (14) above by the data processingdevice 1174, wherein the local calibration matrix C_(L) is used for thecalibration matrix C in equation (14). After the corrected output forcesand/or moments of the applied load are determined by the data processingdevice 1174 in step 1684, the load correction process concludes at step1686 in FIG. 74 .

One or more further illustrative embodiments will be described withreference to FIGS. 75-80 . In these one or more further illustrativeembodiments, a force measurement system, which may be in the form of theforce measurement system 1700, 1700′ depicted in FIGS. 75 and 76includes a force measurement assembly 1710, 1710′ and a data processingdevice 1716, wherein the data processing device 1716 is configured todetermine a center of pressure for the subject 1728 using the outputforces and/or moments from the force measurement assembly 1710, 1710′.The center of pressure for the subject 1728 may be computed in themanner described above. In these one or more further illustrativeembodiments, the force measurement system 1700, 1700′ further includesan inertial measurement unit 1727 and/or camera 1729 configured togenerate output data for determining one or more parameters indicativeof the body sway of the subject 1728 and a mobile device 1726 having abuilt-in data processor (see FIGS. 75 and 76 ). The data processor ofthe mobile device 1726 is operatively coupled to the inertialmeasurement unit 1727 and/or camera 1729, the data processor beingconfigured to receive the output data from the inertial measurement unit1727 and/or camera 1729, and to determine the one or more parametersindicative of the body sway of the subject 1728. In these one or morefurther illustrative embodiments, a fall risk of the subject 1728 may beassessed based upon a combination of the computed center of pressure andthe one or more parameters indicative of the body sway determined forthe subject 1728. Also, in these one or more further illustrativeembodiments, the center of pressure for the subject 1728 determined bythe data processing device 1716 may be independently computed from theone or more parameters indicative of the body sway for the subject 1728determined by the mobile device 1726.

In the illustrative embodiment of FIGS. 75 and 76 , the forcemeasurement system 1700, 1700′ further comprises a visual display device1718 operatively coupled to the data processing device 1716 (e.g., acomputing device or a small-form-factor personal computer, such as theIntel® NUC). The small-form-factor personal computer 1716 is oneillustrative form of a data processing device and/or data processing anddata acquisition device. In FIGS. 75 and 76 , the small-form-factorpersonal computer 1716 may be mounted on the back of the visual displaydevice 1718 (e.g., mounted on the back panel of a touchscreen visualdisplay device with output screen 1720). In one or more embodiments, thescreen images described hereinafter are displayed on the output screen1720 of the visual display device 1718 so that the subject 1728 is ableto interact with one or more visual objects in the screen images.

In the illustrative embodiment of FIGS. 75 and 76 , the visual displaydevice 1718 is disposed on an adjustable height stand or cart 1714 sothat the height of the visual display device 1718 is selectivelyadjustable by a user. Advantageously, prior to a testing session of thesubject 1728, the height of the stand 1714 may be adjusted such that theapproximate center of the visual display device 1718 is generallyhorizontally aligned with the eyes of the standing subject (i.e., so thesubject is generally looking at the central portion of the visualdisplay device 1718 during the testing).

Referring again to FIGS. 75 and 76 , it can be seen that theillustrative force measurement systems 1700, 1700′ include a forcemeasurement assembly 1710, 1710′ for determining the center of pressureof the subject 1728. In particular, the force measurement assembly 1710,1710′ may comprise a static force plate that is configured to rest onthe floor of the room in which the system 1700, 1700′ is disposed (seeFIGS. 75 and 76 ). As will be described in further detail hereinafter,the force plate 1710, 1710′ comprises a plurality of force transducersor load cells for measuring the forces and/or moments generated on theplate surface thereof by the feet of the subject 1728. As such, thecenter of pressure (COP), center of gravity (COG), and/or sway angle ofthe subject 1728 may be determined while the subject 1728 undergoestesting on the force measurement assembly 1710, 1710′.

In addition, as illustrated in FIGS. 75 and 76 , the force measurementassembly 1710, 1710′ is operatively coupled to the data processingdevice 1716 by virtue of an electrical cable 1712. In one embodiment,the electrical cable 1712 is used for data transmission, as well as forproviding power to the force measurement assembly 1710, 1710′. Varioustypes of data transmission cables can be used for cable 1712. Forexample, the cable 1712 can be a Universal Serial Bus (USB) cable or anEthernet cable. Preferably, the electrical cable 1712 contains aplurality of electrical wires bundled together, with at least one wirebeing used for power and at least another wire being used fortransmitting data. The bundling of the power and data transmission wiresinto a single electrical cable 1712 advantageously creates a simpler andmore efficient design. In addition, it enhances the safety of thetraining environment for the subject 1728. However, it is to beunderstood that the force measurement assembly 1710, 1710′ can beoperatively coupled to the data processing device 1716 using othersignal transmission means, such as a wireless data transmission system.If a wireless data transmission system is employed, it is preferable toprovide the force measurement assembly 1710, 1710′ with a separate powersupply in the form of an internal power supply or a dedicated externalpower supply.

Now, with reference to FIGS. 77 and 78 , a first illustrative type offorce measurement assembly 1710 that may be used in the forcemeasurement systems 1700, 1700′ of FIGS. 75 and 76 will be described. Asshown in FIGS. 77 and 78 , the force measurement assembly 1710 of theillustrated embodiment is in the form of a force plate assembly with asingle, continuous measurement surface that measures the vertical force(i.e., F_(Z)) exerted thereon by the subject 1728. The center ofpressure (COP) for the subject 1728 may be computed based upon thefraction of the vertical force that is measured by the load cells ineach of the corners of the force measurement assembly 1710. The forceplate assembly 1710 includes a plate component 1730 supported on aplurality of force transducer beams 1732. As shown in FIGS. 77 and 78 ,the plate component 1730 comprises a top measurement surface (i.e., aplanar top surface) and a plurality of side surfaces extending downwardfrom the top measurement surface. In FIGS. 77 and 78 , it can be seenthat the bottom surface of the plate component 1730 comprises a firstplurality of beam fastener standoffs 1736 and a second plurality ofcover fastener standoffs 1738 extending downward from the bottom surfaceof the plate component 1730. The first plurality of beam fastenerstandoffs 1736 are used to secure the force transducer beams 1732 to theplate component 1730 (i.e., the first plurality of beam fastenerstandoffs 1736 together with the securement nuts 1740 secure the forcetransducer beams 1732 to the underside of the plate component 1730). Thesecond plurality of cover fastener standoffs 1738 are used to secure thebottom cover (not shown) of the force plate assembly 1710 to theunderside of the plate component 1730.

In the illustrative embodiment of FIGS. 77 and 78 , each of the forcetransducer beams 1732 is generally in the form of a linear forcetransducer beam with load cells disposed at the opposite ends of thebeam 1732. Each of the load cells measures the vertical force (i.e.,F_(Z)) exerted on the plate component 1730 by the subject 1728. Also, asbest shown in FIG. 78 , each of the load cells is provided with agenerally rectangular aperture 1734 disposed through the beam 1732. Theapertures 1734 significantly increase the sensitivity of the forcetransducer beam 1732 when a load is applied thereto by reducing thecross-sectional area of the transducer beam 1732 at the locations of theapertures 1734. Referring again to FIG. 78 , it can be seen that each ofthe force transducer beams 1732 comprises a raised portion or standoffportion 1733 so as to ensure that the total load applied to the platecomponent 1730 is transmitted through the load cells of the forcetransducer beams 1732. While not explicitly shown in the figures, it isto be understood that each of the load cells of the force transducerbeams 1732 include strain gages mounted on the outer surfaces of theforce transducer beams 1732 and centered on the apertures 1734 asdescribed above for the preceding load transducer embodiments (see e.g.,FIGS. 26, 29, 33, 39 ).

Referring again to FIGS. 77 and 78 , it can be seen that the forcemeasurement assembly 1710 further includes a pre-amplifier board 1748for digitizing and conditioning the force output signal from the loadcells, and one or more Universal Serial Bus (USB) ports 1746 foroperatively coupling the force measurement assembly 1710 to the dataprocessing device 1716 (i.e., the electrical cable 1712 may have a USBplug that is inserted into one of the USB ports 1746). As shown in theexploded view of FIG. 78 , the pre-amplifier board 1748 may be securedto the plate component 1730 of the force measurement assembly 1710 bymeans of securement screws 1742. In one or more embodiments, thepre-amplifier board 1748 also may compute the output forces, the outputmoments, and/or the center of pressure, and then the data processingdevice 1716 may perform the remainder of the computations that use theoutput forces, the output moments, and/or the center of pressure.

Also, as shown in FIGS. 77 and 78 , the force measurement assembly 1710is provided with a plurality of support feet 1744 disposed thereunder.Preferably, each of the four (4) corners of the force measurementassembly 1710 is provided with a support foot 1744 (e.g., mounted on thebottom corner of each force transducer beam 1732. In particular, in theillustrated embodiment, each support foot 1744 is attached to anaperture in a respective corner of one of the force transducer beams1732 by means of a fastener (e.g., a screw).

With reference again to FIG. 78 , it can be seen that the load cellswith apertures 1734 are located predetermined distances from the footmembers 1744 at the ends of the force transducer beams 1732 so that theload measurement (i.e., of the vertical force F_(Z)) is not affected bystress concentrations on the force transducer beams 1732 resulting frommoments developed at the locations of the foot members 1744. Forexample, as shown in FIG. 78 , the center of the load cell aperture 1734at the left end of the rearward force transducer beam 1732 is located apredetermined distance D1 (e.g., approximately 48 millimeters) from theend of the beam 1732, and the center of the load cell aperture 1734 islocated a predetermined distance D2 (e.g., approximately 35 millimeters)from the end of the raised portion or standoff portion 1733 of the beam1732. In the illustrative embodiment, the distances D1, D2 have beenoptimized to avoid the edge effects associated with the foot member 1744(i.e., the accuracy of the load cell output is not adversely affected byany moment that develops at the foot member 1744 as long as the loadcell is located a sufficient distance D1 away from the end of the beam1732 with the foot member 1744). Also, in the illustrative embodiment,the distances D1, D2 have been optimized to maximize the naturalfrequency of the force measurement assembly 1710. A larger value of D1minimizes the edge effects because load cell is further away from theend of the beam 1732. However, a larger value of D1 results in a longerbeam 1732 that reduces the natural frequency of the force measurementassembly 1710, and thus results in more noise. As such, the distancesD1, D2 are optimized so as to result in an overall beam length thatminimizes edge effects, while simultaneously minimizing noise in theload measurement.

In other embodiments, a foot member with a rounded bottom surface canalso be used to eliminate the development of a moment at the end of theforce transducer beam 1732 (the foot member with a rounded bottomsurface allows the force transducer beam 1732 to behave like acantilever beam). However, the optimization of the distances D1, D2advantageously eliminates the need for a foot with a rounded bottomsurface so that foot members 1744 with the flat bottom surfacesillustrated in FIGS. 77 and 78 may be used.

Next, with reference to FIGS. 79 and 80 , a second illustrative type offorce measurement assembly 1710′ that may be used in the forcemeasurement systems 1700, 1700′ of FIGS. 75 and 76 will be described.With reference to these figures, it can be seen that, in some respects,the second illustrative embodiment is similar to that of the firstillustrative embodiment of the force measurement assembly 1710 describedabove. Moreover, some parts are common to both such embodiments. For thesake of brevity, the description of the parts that the second embodimentof the force measurement assembly has in common with the firstembodiment will not be repeated with regard to the second embodimentbecause these components have already been explained in detail above.Furthermore, in the interest of clarity, these components will bedenoted using the same reference characters that were used in the firstembodiment.

Turning to FIGS. 79 and 80 , it can be seen that the second illustrativetype of force measurement assembly 1710′ utilizes a different type offorce transducer beam 1750 than the force measurement assembly 1710described above. More specifically, rather than using a force transducerbeam that measures only a single force component, the force measurementassembly 1710′ utilizes a multi-component force transducer beam 1750that measures both the vertical force and the shear forces. In theillustrative embodiment of FIGS. 79 and 80 , each of the forcetransducer beams 1750 has a linear middle portion with generallyU-shaped opposed end portions. In the illustrative embodiment, thegenerally U-shaped end portions of the force transducer beams 1750 eachcontain three (3) load cells. Also, as best shown in FIG. 80 , each ofthe load cells is provided with generally rectangular apertures 1752,1754, 1756 disposed through the beam 1750. The first aperture 1752 isassociated with the load cell that measures the vertical force (i.e.,F_(Z)). The second aperture 1754 is associated with the load cell thatmeasures the first shear force (i.e., F_(X)), while the third aperture1756 is associated with the load cell that measures the second shearforce (i.e., F_(Y)). The apertures 1752, 1754, 1756 significantlyincrease the sensitivity of the force transducer beam 1750 when a loadis applied thereto by reducing the cross-sectional area of thetransducer beam 1750 at the locations of the apertures 1752, 1754, 1756.Referring again to FIG. 80 , it can be seen that each of the forcetransducer beams 1750 comprises a raised portion or standoff portion1751 so as to ensure that the total load applied to the plate component1730 is transmitted through the load cells of the force transducer beams1750. While not explicitly shown in the figures, it is to be understoodthat each of the load cells of the force transducer beams 1750 includestrain gages mounted on the outer surfaces of the force transducer beams1750 and centered on the apertures 1752, 1754, 1756 as described abovefor the preceding load transducer embodiments (see e.g., FIGS. 26, 29,33, 39 ).

In the force measurement systems 1700, 1700′ of FIGS. 75 and 76 , themobile device with the data processor is in the form of a smartphone1726. However, in other embodiments, the mobile device also may be inthe form of a tablet computing device, a laptop computing device, or asmartwatch. For example, in the illustrative embodiment, the inertialmeasurement unit 1727 and/or camera 1729 of the force measurementsystems 1700, 1700′ may comprise the built-in inertial measurement unitand/or camera of the smartphone 1726. In another illustrativeembodiment, rather than a mobile computing device, another type ofcomputing device is used. For example, the other type of computingdevice may be a desktop computing device, a tower computing device, aserver computing device, or a small-form-factor personal computer.

In the illustrative embodiment of FIG. 75 , the mobile device 1726(e.g., the smartphone) comprises the inertial measurement unit 1727configured to generate the output data for determining the one or moreparameters indicative of the body sway of the subject 1728 (i.e., thebuilt-in inertial measurement unit 1727 of the smartphone 1726 isutilized). In this illustrative embodiment, the data processor of themobile device 1726 is configured to determine the one or more parametersindicative of the body sway of the subject 1728 based upon the outputdata from the inertial measurement unit 1727 of the mobile device 1726.In the illustrative embodiment, the inertial measurement unit 1727comprises at least one of an accelerometer configured to detect linearacceleration and a gyroscope configured to detect angular velocity.

For example, as part of the sway analysis, the inertial measurement unit1727 (i.e., IMU 1727) is capable of measuring gravitational and motioncomponents. The gravitational component makes it possible to define atrue vertical vector. The body sway is the angle and translation made bythe IMU 1727 around that true vertical. The calculation for the bodysway can be done by a principal component analysis (PCA) to approximatethe area of body sway excursion (i.e., the body sway envelope) asfollows:

$\begin{matrix}{\sigma_{xy}^{2} = {\frac{1}{N - 1}{\sum\limits_{i = j}^{N}{\left( {x_{i} - \overset{\_}{x}} \right)\left( {y_{i} - \overset{\_}{y}} \right)}}}} & (22) \\{{\tan\;\theta} = \frac{\sigma_{xy}^{2}}{\sigma_{0}^{2} - \sigma_{yy}^{2}}} & (23)\end{matrix}$where θ in equation (23) above is the body sway angle. In theillustrative embodiment, the computation of the principal componentanalysis (PCA) set forth in equation (22) may be computed for each jointof the subject 1728.

In one alternative embodiment, the inertial measurement unit that isconfigured to generate the output data for determining the one or moreparameters indicative of the body sway of the subject 1728 is locatedremotely from the mobile device 1726, rather than being a part of mobiledevice 1726. In this alternative embodiment, the data processor of themobile device 1726 is configured to determine the one or more parametersindicative of the body sway of the subject 1728 based upon the outputdata from the remotely located inertial measurement unit. In thisalternative embodiment, the data processor of the mobile device 1726 maybe operatively coupled to the remotely located inertial measurement unitby a wireless connection.

In the illustrative embodiment of FIG. 76 , the mobile device 1726(e.g., the smartphone) comprises the camera 1729 configured to generatethe output data for determining the one or more parameters indicative ofthe body sway of the subject 1728 (i.e., the built-in camera 1729 of thesmartphone 1726 is utilized). For example, the mobile device 1726 (e.g.,the smartphone) may be held by a remote observer 1725, and the camera1729 of the mobile device 1726 may be focused on the subject 1728. Asthe subject's body moves due to his or her sway, the image of thesubject 1728 is captured by the camera 1729 so that the one or moreparameters indicative of the body sway of the subject 1728 may bedetermined from the image data of the camera 1729.

In the illustrative embodiment of FIG. 76 , the data processor of themobile device 1726 may be configured to determine the one or moreparameters indicative of the body sway of the subject 1728 based uponthe output data from the camera 1729 using pose estimation. For example,as part of the sway analysis, the camera 1729 is capable of capturingimage data of the subject 1728. Then, the data processor of the mobiledevice 1726 receives the image data of the subject 1728 from the camera1729. After receiving the image data, the data processor of the mobiledevice 1726 may then extract features from the image data for providinginputs to a convolutional neural network (CNN). After this step, thedata processor of the mobile device 1726 may generate one or morekeypoints using a keypoint subnet, and determine one or more poses ofthe subject 1728 based upon the position of the keypoints.

In one alternative embodiment, the camera that is configured to generatethe output data for determining the one or more parameters indicative ofthe body sway of the subject 1728 is located remotely from the mobiledevice 1726, rather than being a part of mobile device 1726. In thisalternative embodiment, the data processor of the mobile device 1726 isconfigured to determine the one or more parameters indicative of thebody sway of the subject 1728 based upon the output data from theremotely located camera. In this alternative embodiment, the dataprocessor of the mobile device 1726 may be operatively coupled to theremotely located camera by a wireless connection.

Also, in the illustrative embodiment, using the pose estimationdescribed above, the data processor of the mobile device 1726 maydetermine a displacement curve for any of the keypoints of the user(e.g., a displacement curve for the shoulder joint, elbow joint, kneejoint, ankle joint, etc.).

In the illustrative embodiments of FIGS. 75 and 76 , the one or moreparameters indicative of the body sway of the subject 1728 determined bythe data processor of the mobile device 1726 are selected from the groupconsisting of: (i) a sway angle of the subject, (ii) sway coordinates ofthe subject, (iii) a sway envelope of the subject.

In the illustrative embodiments of FIGS. 75 and 76 , the data processingdevice 1716 and/or the mobile device 1726 is programmed to determine amathematical relationship between the center of pressure and the one ormore parameters indicative of the body sway for the subject 1728 over apredetermined time period. For example, with regard to the body sway ofthe subject 1728, the motion of the subject 1728 is modeled as aninverted pendulum with an imaginary vertical line extending lengthwisealong the body of the subject 1728. Using the inverted pendulum model,the mathematical relationship that is determined between the center ofpressure and the one or more parameters indicative of the body sway forthe subject 1728 may be a comparison between the location of one or morecoordinate points on the imaginary vertical line extending along thesubject 1728 (e.g., one or points proximate to, or higher than thecenter of gravity (COG) of the subject 1728) and the center of pressureof the subject 1728. Also, in the illustrative embodiments of FIGS. 75and 76 , the data processing device 1716 and/or the mobile device 1726is programmed to determine the fall risk of the subject 1728 based uponthe mathematical relationship between the center of pressure and the oneor more parameters indicative of the body sway over the predeterminedtime period. For example, using the inverted pendulum model, the dataprocessing device 1716 and/or the mobile device 1726 may estimate thefall risk of the subject 1728 by determining if the one or morecoordinate points on the imaginary vertical line extending along thesubject 1728 (e.g., one or points proximate to, or higher than thecenter of gravity (COG) of the subject 1728) lags behind the center ofpressure of the subject 1728 (a large lag value indicates that thesubject 1728 is likely to fall).

In the illustrative embodiments of FIGS. 75 and 76 , the output forcesand/or moments determined by the data processing device 1716 from theforce measurement assembly 1710, 1710′ include a shear force in afore/aft direction of the subject 1728, and the data processing device1716 is further configured to determine a center of pressure for thesubject 1716 using the output forces and/or moments from the forcemeasurement assembly. In these illustrative embodiments, the dataprocessing device 1716 is additionally configured to determine the fallrisk of the subject 1728 based upon a combination of the center ofpressure and the shear force in the fore/aft direction of the subject1728. For example, the data processing device 1716 may evaluate themaximum sway range of the center of pressure of the subject 1728 and themagnitude of the shear force in a fore/aft direction of the subject 1728in order to assess the fall risk of the subject 1728. If both the valueof the maximum sway range of the center of pressure of the subject 1728and the value of the shear force in a fore/aft direction of the subject1728 are large in magnitude, then the data processing device 1716 mayconclude the subject is highly likely to sustain a fall. If at least oneof the maximum sway range of the center of pressure of the subject 1728and the shear force in a fore/aft direction of the subject 1728 is largein magnitude, then the data processing device 1716 may conclude thesubject is likely to sustain a fall. If both the value of the maximumsway range of the center of pressure of the subject 1728 and the valueof the shear force in a fore/aft direction of the subject 1728 are smallin magnitude, then the data processing device 1716 may conclude thesubject is unlikely to sustain a fall.

In one variation of the illustrative embodiments of FIGS. 75 and 76 ,the data processing device 1716 and/or the mobile device 1726 is furtherprogrammed to determine the fall risk of the subject based upon arelationship between the one or more parameters indicative of the bodysway for the subject 1728 determined by the mobile device 1726 and theshear force in the fore/aft direction of the subject 1728 determined bythe data processing device 1716 from the output data of the forcemeasurement assembly 1710, 1710′. For example, the data processingdevice 1716 and/or the mobile device 1726 may evaluate the magnitude ofthe maximum sway angle for the subject 1728 and the magnitude of theshear force in a fore/aft direction of the subject 1728 in order toassess the fall risk of the subject 1728. If both the value of themaximum sway angle of the subject 1728 and the value of the shear forcein a fore/aft direction of the subject 1728 are large in magnitude, thenthe data processing device 1716 and/or the mobile device 1726 mayconclude the subject is highly likely to sustain a fall. If at least oneof the maximum sway angle of the subject 1728 and the shear force in afore/aft direction of the subject 1728 is large in magnitude, then thedata processing device 1716 and/or the mobile device 1726 may concludethe subject is likely to sustain a fall. If both the value of themaximum sway angle of the subject 1728 and the value of the shear forcein a fore/aft direction of the subject 1728 are small in magnitude, thenthe data processing device 1716 and/or the mobile device 1726 mayconclude the subject is unlikely to sustain a fall.

Referring again to FIG. 75 , in the illustrative embodiment, the visualdisplay device 1718 of the illustrative force measurement systems 1700,1700′ may be configured to display at least one manipulatable element(e.g., an airplane 1722) of an interactive game on the output screen sothat the at least one manipulatable element is visible to the subject1728. In the illustrative embodiment, the data processing device 1716and/or the mobile device 1726 is programmed to control the movement ofthe at least one manipulatable element (e.g., an airplane 1722) of theinteractive game displayed on the visual display device 1718 by usingthe center of pressure and the one or more parameters indicative of thebody sway for the subject 1728 (e.g., if the user leans forward, theairplane decreases in altitude, while, if the user leans backward, theairplane increases in altitude). In the exemplary interactive game, thefore/aft leaning of the subject 1728 could guide the airplane 1722through rings or hoops 1724 located at different altitudes in the sky.In the illustrative embodiment, the data processing device 1716 and/orthe mobile device 1726 may be further programmed to determine the fallrisk of the subject 1728 based upon the performance of the subject 1728while playing the interactive game (e.g., in the airplane game, the fallrisk of the subject 1728 may increase as the number of rings or hoopsmissed by the subject 1728 increases).

In an alternative embodiment, rather than using the mobile device 1726to determine the one or more parameters indicative of the body sway forthe subject 1728, other suitable means may be used for determining theone or more body sway parameters. For example, to measure the body swayof the subject 1728, one end of an extendable elongated attachmentmember (e.g., a string) may be attached to the belt of the subject 1728,and the other fixed end of the extendable elongated attachment member(e.g., the string) may be attached to a goniometer (e.g., similar to anextendable dog leash). As another example, to measure the body sway ofthe subject 1728, a distance measuring laser targeting the mid-portionof the subject 1728 may be used. Also, rather than using a distancemeasuring laser, an infrared detector or ultrasonic detector may be usedto measure the distance to the mid-portion of the subject 1728.

FIGS. 81-83 illustrate a force measurement assembly 1800 according to afurther embodiment of the present invention. In the illustrativeembodiment, the force measurement assembly 1800 of FIGS. 81-83 may beprovided as part of a force measurement system, and thus may beoperatively coupled to a data acquisition/data processing device (i.e.,the data acquisition/data processing device 1174 described inconjunction with FIG. 42 above). The functionality of the forcemeasurement system comprising the force measurement assembly 1800 andthe data acquisition/data processing device would be generally the sameas that described above for the embodiment of FIGS. 42 and 43 , and thusneed not be reiterated in conjunction with the description of the forcemeasurement assembly 1800 of FIGS. 81-83 . Also, like the forcemeasurement assembly 1150 described above, the force measurementassembly 1800 illustrated in FIGS. 81-83 is configured to receive auser/subject thereon, and is capable of measuring the forces and/ormoments applied to its measurement surface by the user/subject.

Referring again to FIGS. 81-83 , it can be seen that the forcemeasurement assembly 1800 of the illustrated embodiment is in the formof a force plate assembly with a top measurement surface. The forceplate assembly includes a top base plate 1814 supported on a pluralityof load transducer beams 1802, 1804. In the illustrated embodiment, eachload transducer beam 1802, 1804 may be mounted to the underside of thetop base plate 1814 by a respective mounting plate 1806. Also, as shownin FIGS. 81-83 , the force measurement assembly 1800 further comprisesan outer top plate component 1816 that is supported on the top baseplate 1814. In the illustrated embodiment, the top base plate 1814 maybe formed from aluminum. In the illustrated embodiment, the outer topplate component 1816 may be formed from a suitable polymeric material orplastic (e.g., injection-molded plastic), and may be clipped onto thetop base plate 1814.

In illustrated embodiment of FIGS. 81-83 , the force measurementassembly 1800 comprises a pair of spaced-apart load transducer beams1802, 1804 that are disposed underneath, and near each of the respectivesides of the outer top plate component 1816. In the illustrativeembodiment of FIGS. 81-83 , each of the force transducer beams 1802,1804 is generally in the form of a linear force transducer beam withload cells disposed at the opposite ends of the beam 1802, 1804. In theillustrated embodiment, the frame portion of each load transducer 1802,1804 is milled as one solid and continuous piece of a single material.That is, the frame portion of the load transducer beam 1802, 1804 is ofunitary or one-piece construction. The frame portion of the loadtransducer beam 1802, 1804 is preferably machined in one piece fromaluminum, titanium, steel, or any other suitable material that meetsstrength and weight requirements.

Also, as depicted in FIGS. 81 and 82 , the load transducer beams 1802,1804 each comprise a plurality of mounting apertures 1812 (e.g., a pairof mounting apertures 1812) disposed therethrough near the respectivebeam ends for accommodating fasteners (e.g., screws) that attach theload transducer beams 1802, 1804 to mounting feet of the force plate orforce measurement assembly. The load applied to the load transducerbeams 1802, 1804 is conveyed through the plurality of beam portionsbetween the mounting plates 1806 and the mounting feet.

Referring collectively to FIGS. 81 and 82 , it can be seen that aplurality of deformation sensing elements (e.g., strain gages 1808,1810) are disposed on the outer surfaces of the frame portions of theload transducer beams 1802, 1804. In particular, in the illustrativeembodiment, the strain gages 1810 disposed on the top surfaces of theload transducer beams 1802, 1804 (see FIG. 82 ) are sensitive to a firstforce component (i.e., the z-component of the force, F_(Z)) of the loadand output one or more first output signals representative of the firstforce component (F_(Z)) or vertical force (F_(Z)). Also, in theillustrative embodiment, the strain gages 1808 disposed on the inwardlyfacing side surfaces of the load transducer beams 1802, 1804 (see FIG.81 ) are sensitive to a second force component (i.e., the x-component ofthe force, F_(X)) of the load and output one or more second outputsignals representative of the second force component (F_(X)) or shearforce (F_(X)) in a lateral direction. In the illustrative embodiment,the inwardly facing side surface of the load transducer beam 1802, 1804on which the strain gages 1808 are disposed is perpendicular orgenerally perpendicular to the top surface of the load transducer beam1802, 1804 on which the strain gages 1810 are disposed. Also, in theillustrative embodiment, the first output signals from the strain gages1810 may be used to determine a center of pressure for the user/subject.More specifically, referring to the perspective view of FIG. 81 , it canbe seen that the center of pressure coordinates (x_(P), y_(P)) for theforce measurement assembly 1800 may be determined in accordance with xand y coordinate axes 1866, 1868. In FIG. 81 , the vertical component ofthe force (F_(Z)) is defined by the z coordinate axis 1870.

In the illustrative embodiment, the strain gages 1808, 1810 in eachstrain gage pair at the ends of the load transducer beams 1802, 1804 maybe spaced apart from one another by a distance of approximately 1.0 to2.0 inches, or more preferably, a distance of approximately 1.5 inches.

FIGS. 84-86 illustrate a force measurement assembly 1820 according toyet a further embodiment of the present invention. In the illustrativeembodiment, similar to the force measurement assembly 1800 describedabove, the force measurement assembly 1820 of FIGS. 84-86 may beprovided as part of a force measurement system, and thus may beoperatively coupled to a data acquisition/data processing device (i.e.,the data acquisition/data processing device 1174 described inconjunction with FIG. 42 above). The functionality of the forcemeasurement system comprising the force measurement assembly 1820 andthe data acquisition/data processing device would be generally the sameas that described above for the embodiment of FIGS. 42 and 43 , and thusneed not be reiterated in conjunction with the description of the forcemeasurement assembly 1820 of FIGS. 84-86 . Also, like the forcemeasurement assembly 1150 described above, the force measurementassembly 1820 illustrated in FIGS. 84-86 is configured to receive auser/subject thereon, and is capable of measuring the forces and/ormoments applied to its measurement surface by the user/subject.

Referring again to FIGS. 84-86 , it can be seen that the forcemeasurement assembly 1820 of the illustrated embodiment is in the formof a force plate assembly with a top measurement surface. The forceplate assembly includes a top base plate 1834 supported on a pluralityof load transducer beams 1822, 1824. In the illustrated embodiment, eachload transducer beam 1822, 1824 may be mounted to the underside of thetop base plate 1834 by a respective mounting plate 1826. Also, as shownin FIGS. 84-86 , the force measurement assembly 1820 further comprisesan outer top plate component 1836 that is supported on the top baseplate 1834. In the illustrated embodiment, the top base plate 1834 maybe formed from aluminum. In the illustrated embodiment, the outer topplate component 1836 may be formed from a suitable polymeric material orplastic (e.g., injection-molded plastic), and may be clipped onto thetop base plate 1834,

In illustrated embodiment of FIGS. 84-86 , the force measurementassembly 1820 comprises a pair of spaced-apart load transducer beams1822, 1824 that are disposed underneath, and near each of the respectivesides of the outer top plate component 1836. In the illustrativeembodiment of FIGS. 84-86 , each of the force transducer beams 1822,1824 is generally in the form of a linear force transducer beam withload cells disposed at the opposite ends of the beam 1822, 1824. In theillustrated embodiment, the frame portion of each load transducer 1822,1824 is milled as one solid and continuous piece of a single material.That is, the frame portion of the load transducer beam 1822, 1824 is ofunitary or one-piece construction. The frame portion of the loadtransducer beam 1822, 1824 is preferably machined in one piece fromaluminum, titanium, steel, or any other suitable material that meetsstrength and weight requirements.

Also, as depicted in FIGS. 84 and 85 , the load transducer beams 1822,1824 each comprise a plurality of mounting apertures 1832 (e.g., a pairof mounting apertures 1832) disposed therethrough near the respectivebeam ends for accommodating fasteners (e.g., screws) that attach theload transducer beams 1822, 1824 to mounting feet of the force plate orforce measurement assembly. The load applied to the load transducerbeams 1822, 1824 is conveyed through the plurality of beam portionsbetween the mounting plates 1826 and the mounting feet.

Referring collectively to FIGS. 84-86 , it can be seen that a pluralityof deformation sensing elements (e.g., strain gages 1828, 1830) aredisposed on the outer surfaces of the frame portions of the loadtransducer beams 1822, 1824. In particular, in the illustrativeembodiment, the strain gages 1830 disposed on the top surfaces of theload transducer beams 1822, 1824 (see FIG. 85 ) are sensitive to a firstforce component (i.e., the z-component of the force, F_(Z)) of the loadand output one or more first output signals representative of the firstforce component (F_(Z)) or vertical force (F_(Z)). Also, in theillustrative embodiment, the strain gages 1828 disposed on the inwardlyfacing side surfaces of the load transducer beams 1822, 1824 (see FIGS.84 and 86 ) are sensitive to a second force component (i.e., they-component of the force, F_(Y)) of the load and output one or moresecond output signals representative of the second force component(F_(Y)) or shear force (F_(Y)) in a fore/aft direction. In theillustrative embodiment, the inwardly facing side surface of the loadtransducer beam 1820, 1824 on which the strain gages 1828 are disposedis perpendicular or generally perpendicular to the top surface of theload transducer beam 1822, 1824 on which the strain gages 1830 aredisposed. Also, in the illustrative embodiment, the first output signalsfrom the strain gages 1830 may be used to determine a center of pressurefor the user/subject. More specifically, referring to the perspectiveview of FIG. 84 , it can be seen that the center of pressure coordinates(x_(P), y_(P)) for the force measurement assembly 1820 may be determinedin accordance with x and y coordinate axes 1866, 1868. In FIG. 84 , thevertical component of the force (F_(Z)) is defined by the z coordinateaxis 1870.

In the illustrative embodiment, the strain gages 1828, 1830 in eachstrain gage pair at the ends of the load transducer beams 1822, 1824 maybe spaced apart from one another by a distance of approximately 1.0 to2.0 inches, or more preferably, a distance of approximately 1.5 inches.

FIGS. 87-89 illustrate a force measurement assembly 1820 according toyet a further embodiment of the present invention. In the illustrativeembodiment, the force measurement assembly 1840 of FIGS. 87-89 may beprovided as part of a force measurement system, and thus may beoperatively coupled to a data acquisition/data processing device (i.e.,the data acquisition/data processing device 1174 described inconjunction with FIG. 42 above). The functionality of the forcemeasurement system comprising the force measurement assembly 1840 andthe data acquisition/data processing device would be generally the sameas that described above for the embodiment of FIGS. 42 and 43 , and thusneed not be reiterated in conjunction with the description of the forcemeasurement assembly 1840 of FIGS. 87-89 . Also, like the forcemeasurement assembly 1150 described above, the force measurementassembly 1840 illustrated in FIGS. 87-89 is configured to receive auser/subject thereon, and is capable of measuring the forces and/ormoments applied to its measurement surface by the user/subject.

Referring again to FIGS. 87-89 , it can be seen that the forcemeasurement assembly 1840 of the illustrated embodiment is in the formof a force plate assembly with a top measurement surface. The forceplate assembly includes a top base plate 1862 supported on a pluralityof load transducer beams 1842, 1844, 1846, 1848. In the illustratedembodiment, each load transducer beam 1842, 1844, 1846, 1848 may bemounted to the underside of the top base plate 1862 by a respectivemounting plate 1850. Also, as shown in FIGS. 87-89 , the forcemeasurement assembly 1840 further comprises an outer top plate component1864 that is supported on the top base plate 1862. In the illustratedembodiment, the top base plate 1862 may be formed from aluminum. In theillustrated embodiment, the outer top plate component 1864 may be formedfrom a suitable polymeric material or plastic (e.g., injection-moldedplastic), and may be clipped onto the top base plate 1862.

In illustrated embodiment of FIGS. 87-89 , the force measurementassembly 1840 comprises a first pair of spaced-apart load transducerbeams 1842, 1844 that are disposed underneath, and near each of therespective sides of the outer top plate component 1864. In theillustrative embodiment of FIGS. 87-89 , each of the force transducerbeams 1842, 1844 is generally in the form of a linear force transducerbeam with load cells disposed at the opposite ends of the beam 1842,1844. In the illustrated embodiment, the frame portion of each loadtransducer 1842, 1844 is milled as one solid and continuous piece of asingle material. That is, the frame portion of the load transducer beam1842, 1844 is of unitary or one-piece construction. The frame portion ofthe load transducer beam 1842, 1844 is preferably machined in one piecefrom aluminum, titanium, steel, or any other suitable material thatmeets strength and weight requirements.

In illustrated embodiment of FIGS. 87-89 , the force measurementassembly 1840 further comprises a second pair of spaced-apart loadtransducer beams 1846, 1848 that are disposed between the loadtransducer beams 1842, 1844, and are disposed inwardly from the loadcells of load transducer beams 1842, 1844. In the illustrativeembodiment of FIGS. 87-89 , each of the force transducer beams 1846,1846 is generally in the form of a linear force transducer beam withload cells disposed at the opposite ends of the beam 1846, 1848. In theillustrated embodiment, the frame portion of each load transducer 1846,1848 is milled as one solid and continuous piece of a single material.That is, the frame portion of the load transducer beam 1846, 1848 is ofunitary or one-piece construction. The frame portion of the loadtransducer beam 1846, 1848 is preferably machined in one piece fromaluminum, titanium, steel, or any other suitable material that meetsstrength and weight requirements. As shown in FIGS. 87-89 , the endportions of the load transducer beams 1846, 1848 are rigidly connectedto the middle portions of the load transducer beams 1842, 1844 by lowerbeam connector plates 1856 and upper beam connector plates 1858.

In illustrated embodiment, the load transducer beams 1842, 1844, 1846,1848 have a modular construction such that a single load transducer beamof the same type is configured to be interchangeably used for each ofthe load transducer beams 1842, 1844, 1846, 1848 (i.e., a modular loadtransducer beam is able to be positioned in any of the four (4)different positions on the force measurement assembly 1840, and themodular load transducer beam is configured to be combined with the otherload transducer beams on the force measurement assembly 1840 to form thecombined measurement structure). Advantageously, the use of a modularload transducer beam obviates the need for unique parts for each of theload transducer beams 1842, 1844, 1846, 1848).

Also, as depicted in FIGS. 87 and 88 , the load transducer beams 1842,1844 each comprise a plurality of mounting apertures 1860 (e.g., a pairof mounting apertures 1860) disposed therethrough near the respectivebeam ends for accommodating fasteners (e.g., screws) that attach theload transducer beams 1842, 1844 to mounting feet of the force plate orforce measurement assembly.

Referring collectively to FIGS. 87-89 , it can be seen that a pluralityof deformation sensing elements (e.g., strain gages 1852, 1854) aredisposed on the outer surfaces of the frame portions of the loadtransducer beams 1842, 1844, 1846, 1848. In particular, in theillustrative embodiment, the strain gages 1854 disposed on the topsurfaces of the load transducer beams 1842, 1844, 1846, 1848 (see FIG.88 ) are sensitive to a first force component (i.e., the z-component ofthe force, F_(Z)) of the load and output one or more first outputsignals representative of the first force component (F_(Z)) or verticalforce (F_(Z)). Also, in the illustrative embodiment, the strain gages1852 disposed on the inwardly facing side surfaces of the loadtransducer beams 1842, 1844 (see FIG. 87 ) are sensitive to a secondforce component (i.e., the x-component of the force, F_(X)) of the loadand output one or more second output signals representative of thesecond force component (F_(X)) or shear force (F_(X)) in a lateraldirection. In addition, in the illustrative embodiment, the strain gages1852 disposed on the inwardly facing side surfaces of the loadtransducer beams 1846, 1848 (see FIGS. 87 and 89 ) are sensitive to athird force component (i.e., the y-component of the force, F_(Y)) of theload and output one or more third output signals representative of thesecond force component (F_(Y)) or shear force (F_(Y)) in a fore/aftdirection. In the illustrative embodiment, the inwardly facing sidesurface of the load transducer beam 1842, 1844, 1846, 1848 on which thestrain gages 1852 are disposed is perpendicular or generallyperpendicular to the top surface of the load transducer beam 1842, 1844,1846, 1848 on which the strain gages 1854 are disposed. Also, in theillustrative embodiment, the first output signals from the strain gages1854 may be used to determine a center of pressure for the user/subject.More specifically, referring to the perspective view of FIG. 87 , it canbe seen that the center of pressure coordinates (x_(P), y_(P)) for theforce measurement assembly 1840 may be determined in accordance with xand y coordinate axes 1866, 1868. In FIG. 87 , the vertical component ofthe force (F_(Z)) is defined by the z coordinate axis 1870.

Further, in the illustrative embodiment, the data processing device isfurther configured to determine a torque about the vertical axis 1870for the user/subject using the output data from the force measurementassembly 1840 (e.g., in a golf application of the force measurementassembly 1840).

In the illustrative embodiment, the strain gages 1852, 1854 in eachstrain gage pair at the ends of the load transducer beams 1842, 1844,1846, 1848 may be spaced apart from one another by a distance ofapproximately 1.0 to 2.0 inches, or more preferably, a distance ofapproximately 1.5 inches.

One or more further illustrative embodiments will be described withreference to FIGS. 90-97 . In these one or more further illustrativeembodiments, with reference initially to FIG. 93 , the force measurementsystem comprises a plurality of force measurement assemblies 1900 a,1900 b, 1900 c, 1900 d, 1900 e, 1900 f, where at least some of theplurality of force measurement assemblies (e.g., force measurementassemblies 1900 a, 1900 b) are configured to be independentlydisplaceable from other ones of the plurality of force measurementassemblies (e.g., force measurement assemblies 1900 c, 1900 d, 1900 e,1900 f) such that one or more particular ones of the plurality of forcemeasurement assemblies that are disposed underneath a subject variesover time. In these one or more further embodiments, each of theplurality of force measurement assemblies 1900 a, 1900 b, 1900 c, 1900d, 1900 e, 1900 f includes a top surface for receiving at least oneportion of the body of the subject; and at least one force transducer,the at least one force transducer configured to sense one or moremeasured quantities and output one or more signals that arerepresentative of forces and/or moments being applied to the top surfaceof the force measurement assembly by the subject. Also, in these one ormore further embodiments, the force measurement system further comprisesone or more data processing devices operatively coupled to each of theforce transducers of each of the force measurement assemblies, the oneor more data processing devices configured to receive each of the one ormore signals that are representative of the one or more measuredquantities and to convert the one or more signals into load output data,the load output data comprising one or more forces and/or one or moremoments.

An illustrative one 1900 of the independently displaceable forcemeasurement assemblies 1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f isshown in FIGS. 90-92 . With initial reference to the perspective view ofFIG. 90 , it can be seen that the independently displaceable forcemeasurement assembly 1900 includes a force plate 1902 mounted on a topof a displaceable support carriage 1906. The displaceable supportcarriage 1906 is configured to be selectively displaced on a supportsurface (e.g., a floor of a building). In the illustrative embodiment,the force plate 1902 may be attached to the displaceable supportcarriage 1906 by a plurality of fastener members 1904 (e.g., four (4)recessed screws). With combined reference to FIGS. 90-92 , in theillustrative embodiment, the displaceable support carriage 1906comprises a plurality of side panels 1908 and a bottom panel 1910 forcovering internal components (e.g., portions of the wheels 1912, thewheel actuators, etc.) of the support carriage 1906. In the illustrativeembodiment, the force plate 1902 of the force measurement assembly 1900may be in the form of one of the force plates 1710, 1710′, 1800, 1820,1840 described above.

Referring again to FIGS. 90-92 , in the illustrative embodiment, thedisplaceable support carriage 1906 comprises a plurality of wheels 1912disposed on a bottom of the displaceable support carriage 1906 forselectively displacing the force measurement assembly 1900 on thesupport surface. In the illustrative embodiment, the wheels 1912 do notpivot about a vertical axis (i.e., the wheels are non-steerable), and aturning direction of the force measurement assembly 1900 is determinedby selectively activating one or more of the plurality of wheels 1912 ina first rotational direction and selectively activating one or moreother ones of the plurality of wheels 1912 in a second rotationaldirection, where the first rotational direction being opposite to thesecond rotational direction. In the illustrative embodiment, a skidsteering technique may be used for turning the displaceable supportcarriage 1906. For example, when it is desired to turn the displaceablesupport carriage 1906 to the right, the wheels 1912 on the left side ofthe displaceable support carriage 1906 are rotated in a forwarddirection, while the wheels 1912 on the right side of the displaceablesupport carriage 1906 are rotated in a reverse direction. When it isdesired for the displaceable support carriage 1906 to go straight, allof the wheels 1912 are rotated in a forward direction. In theillustrative embodiment, the wheels 1912 are driven in a selectedforward or reverse direction by actuators that are under the control ofthe one or more data processing devices such that the one or more dataprocessing devices are able to control the movement of the individualforce measurement assemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900e, 1900 f in the force measurement system.

In an alternative embodiment, one or more of the plurality of wheels1912 on the displaceable support carriage 1906 are pivotable (i.e.,steerable), and a turning direction of the force measurement assembly1900 is determined by rotating the one or more of the plurality ofwheels 1912 to a selected angular position.

Now, turning to FIGS. 93-96 , a first illustrative arrangement of forcemeasurement assemblies 1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 fwill be described. Initially, in the initial configuration 1920 of FIG.93 , all of the force measurement assemblies 1900 a, 1900 b, 1900 c,1900 d, 1900 e, 1900 f are arranged in a linear configuration. Then, inthe next configuration 1930 of FIG. 94 , it can be seen that therearmost force measurement assembly 1900 a is starting to be displacedalong the side of the other force measurement assemblies 1900 b, 1900 c,1900 d, 1900 e, 1900 f. In the configuration 1940 of FIG. 95 , the forcemeasurement assembly 1900 a has traveled further along the side of theother force measurement assemblies 1900 b, 1900 c, 1900 d, 1900 e, 1900f. Finally, in the configuration 1950 of FIG. 96 , the force measurementassembly 1900 a has reached its final displacement location in front ofthe other force measurement assemblies 1900 b, 1900 c, 1900 d, 1900 e,1900 f.

In the first illustrative arrangement of FIGS. 93-96 , one or more ofthe plurality of force measurement assemblies (e.g., force measurementassembly 1900 a) are configured to be continually displaced from aposterior position behind a subject to an anterior position in front ofthe subject in order to maintain a generally consistent quantity of theplurality of force measurement assemblies disposed underneath thesubject while the subject is walking or running on the plurality offorce measurement assemblies 1900 a, 1900 b, 1900 c, 1900 d, 1900 e,1900 f. In the arrangement of FIGS. 93-96 , when the one or more of theplurality of force measurement assemblies (e.g., force measurementassembly 1900 a) are displaced from the posterior position behind thesubject to the anterior position in front of the subject, the one ormore of the plurality of force measurement assemblies (e.g., forcemeasurement assembly 1900 a) are displaced along a side of the pluralityof force measurement assemblies disposed underneath the subject (e.g.,along a side of the force measurement assemblies 1900 b, 1900 c, 1900 d,1900 e, 1900 f).

A second illustrative arrangement 1960 of force measurement assemblies1900 will be described with reference to FIG. 97 . In the illustrativearrangement 1960 of FIG. 97 , a plurality of independently displaceableforce measurement assemblies 1900 are arranged in a matrix configuration(e.g., a 6×6 matrix containing a total of thirty-six (36) independentlydisplaceable force measurement assemblies 1900). The force measurementassemblies 1900 of the matrix configuration 1960 in FIG. 97 can bedisplaced in a manner similar to that described above for thearrangement of FIGS. 93-96 .

In the force measurement systems of FIGS. 93-96 described above, thereis no physical connection between individual ones of the plurality offorce measurement assemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900e, 1900 f such that the individual ones of the plurality of forcemeasurement assemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900 e,1900 f are capable of being independently displaced along virtually anypath on a support surface. Because the plurality of force measurementassemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f areindependently displaceable while a subject is walking or running on theforce measurement assemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900e, 1900 f, a small footprint of force measurement assemblies 1900, 1900a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f can advantageously be used.

Also, in the force measurement systems of FIGS. 93-96 described above, agap is provided between each of the force measurement assemblies 1900,1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f so as to preventinteraction between adjacent ones of the plurality of force measurementassemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f. The topsurfaces of each of the plurality of force measurement assemblies 1900,1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f remain upwardly facingwhen the plurality of force measurement assemblies 1900, 1900 a, 1900 b,1900 c, 1900 d, 1900 e, 1900 f are being independently displaced. Also,when plurality of force measurement assemblies 1900, 1900 a, 1900 b,1900 c, 1900 d, 1900 e, 1900 f are being independently displaced, thetop surface of each of the plurality of force measurement assemblies1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900 e, 1900 f remains generallyparallel to the top surfaces of the other ones of the plurality of forcemeasurement assemblies 1900, 1900 a, 1900 b, 1900 c, 1900 d, 1900 e,1900 f.

FIGS. 98-101 illustrate a force measurement assembly 2000 according to afurther embodiment of the present invention. As will be described infurther detail hereinafter, in the illustrative embodiment, the forcemeasurement assembly 2000 of FIGS. 98-101 may be provided as part of aforce plate array with a plurality of force plate assemblies (see FIGS.102-105 ). As shown in FIGS. 98-101 , the force measurement assembly2000 comprises a single force transducer 2014 supporting the topcomponent 2002. As such, in this illustrative embodiment, the singleforce transducer 2014 supports the entire weight of the top component2002 and there are no other force transducers disposed underneath thetop component 2002. In the illustrative embodiment, the single forcetransducer 2014 is disposed proximate to a center of the top component2002. In order to support the entire weight of the top component 2002and the subject disposed thereon during the use of the force measurementassembly 2000, the single force transducer 2014 may have an outerdiameter than is between approximately one-third and approximatelyone-half the width dimension of the top component 2002. Similar to theforce measurement assemblies described above, the force measurementassembly 2000 illustrated in FIGS. 98-101 is configured to receive auser/subject thereon, and is capable of measuring the forces and/ormoments applied to its measurement surface by the user/subject.

Referring again to FIGS. 98-101 , it can be seen that the forcemeasurement assembly 2000 of the illustrative embodiment is in the formof a force plate assembly with a top measurement surface. The forceplate assembly includes a top plate 2002 supported on the singlepylon-type load transducer 2014. In the illustrative embodiment, asshown in FIGS. 99 and 100 , the single pylon-type load transducer 2014may be mounted to the underside of the top plate 2002 by means of a topadapter plate 2006. In particular, with combined reference to FIGS.98-101 , it can be seen that the top adapter plate 2006 may be securedto the underside of the top plate 2002 by a plurality of fastenermembers 2012 (e.g., a plurality of machine screws) that are receivedwithin respective apertures 2010 in the top adapter plate 2006.

In illustrative embodiment of FIGS. 98-101 , the force measurementassembly 2000 comprises the single pylon-type load transducer 2014. Theload transducer 2014 generally includes a one-piece compact transducerframe portion having a central cylindrical body portion 2018 and a pairof flanges 2016, 2020 disposed at opposite longitudinal ends of thecentral cylindrical body portion 2018. In particular, the loadtransducer 2014 includes a bottom flange 2020 disposed at the lowerlongitudinal end of the cylindrical body portion 2018, and a top flange2016 disposed at the upper longitudinal end of the cylindrical bodyportion 2018. As best illustrated in the exploded perspective view ofFIG. 101 , the bottom flange 2020 comprises a plurality ofcircumferentially spaced-apart mounting apertures disposed therethrough.Each of the mounting apertures is configured to receive a respectivefastener 2024 (e.g., a threaded screw or bolt) for securing the loadtransducer 2014 to the bottom base plate 2030. In the bottom base plate2030, each of the fasteners 2024 is received in a respective fasteneraperture 2034. As shown in FIG. 101 , in the illustrative embodiment,the top surface of the bottom base plate 2030 is provided with a slightcircular recess 2032 in the center thereof for receiving the bottomportion of the bottom flange 2020 of the load transducer 2014, whichenables the load transducer 2014 to be essentially self-aligned on thebottom base plate 2030. Similarly, as shown in FIG. 101 , the top flange2016 also comprises a plurality of circumferentially spaced-apartmounting apertures disposed therethrough. Each of the mounting aperturesis configured to receive a respective fastener 2004 (e.g., a threadedscrew or bolt) for securing the load transducer 2014 to the top adapterplate 2006. In the top adapter plate 2006, each of the fasteners 2004 isreceived in a respective fastener aperture 2008. Similar to the circularrecess 2032 in the bottom base plate 2030, the bottom surface of the topadapter plate 2006 may be provided with a slight circular recess in thecenter thereof for receiving the top portion of the top flange 2016 ofthe load transducer 2014, which would enable the load transducer 2014also to be essentially self-aligned on the top adapter plate 2006 aswell. The frame portion of the pylon-type load transducer 2014 ispreferably machined in one piece from aluminum, titanium, steel, or anyother suitable material that meets strength and weight requirements.

In illustrative embodiment, with reference again to FIGS. 98 and 101 ,it can be seen that the bottom base plate 2030 may be provided with afirst plurality of mounting apertures 2036 disposed around the circularrecess 2032 for receiving respective fasteners for securing the forcemeasurement assembly 2000 to a support surface (e.g., a floor of abuilding). The first plurality of mounting apertures 2036 are locatedbetween the peripheral edge of the bottom base plate 2030 and thecircular recess 2032. In addition, as further shown in FIGS. 98 and 101, the bottom base plate 2030 may be provided with a second plurality ofmounting apertures 2038 disposed in respective corners of the base plate2030 for receiving respective fasteners for securing the forcemeasurement assembly 2000 to the support surface (e.g., a floor of abuilding).

Referring collectively to FIGS. 99-101 , it can be seen that a pluralityof deformation sensing elements (e.g., strain gages 2022) are disposedon the outer periphery of the central cylindrical body portion 2018 ofthe load transducer 2014. In particular, in the illustrative embodiment,a first subset of the strain gages 2022 (see FIG. 101 ) is sensitive toa first force component (i.e., the z-component of the force, F_(Z),which is the vertical force) of the load and the outputs one or morefirst output signals representative of the first force component(F_(Z)). A second subset of the strain gages 2022 (see FIG. 101 ) issensitive to one or more second force components (i.e., the x-componentor y-component of the force, F_(X), F_(Y), which are the shear forces)of the load and the outputs one or more second output signalsrepresentative of the one or more second force components (F_(X),F_(Y)). In the illustrative embodiment, the load transducer 2014 may bea six-component load transducer that measures all three (3) orthogonalcomponents of the resultant forces and moments acting on the top platecomponent 2002 of the force measurement assembly 2000 (i.e., F_(X),F_(Y), F_(Z), M_(X), M_(Y), M_(Z)). The entire load applied to the topplate component 2002 of the load transducer 2014 is conveyed through thecentral cylindrical body portion 2018 such that the resultingdeformation of the cylindrical body portion 2018 detected by the straingages 2022 is indicative of the applied load to the top plate component2002.

Referring again to FIGS. 98-101 , it can be seen that the forcemeasurement assembly 2000 further includes a printed circuit board (PCB)assembly 2026 for digitizing and conditioning the force output signalfrom the load transducer 2014. The printed circuit board assembly 2026may include one or more Universal Serial Bus (USB) ports for operativelycoupling the force measurement assembly 2000 to an external computingdevice (i.e., an electrical cable connected to the computing device mayhave a USB plug that is inserted into one of the USB ports of theprinted circuit board assembly 2026). As shown in FIGS. 98-101 , theprinted circuit board assembly 2026 may be secured to the bottom baseplate 2030 of the force measurement assembly 2000 by means of securementscrews 2028 and threaded standoffs 2029. The threaded standoffs 2029elevate the printed circuit board assembly 2026 slightly above the topsurface of the bottom base plate 2030, and the securement screws 2028fasten the printed circuit board assembly 2026 to the threaded standoffs2029. In the illustrative embodiment, the threaded standoffs 2029 aresecured into the top surface of the bottom base plate 2030. In one ormore embodiments, the printed circuit board assembly 2026 also maycompute the output forces, the output moments, and/or the center ofpressure, and then the external computing device may perform theremainder of the computations that use the output forces, the outputmoments, and/or the center of pressure from the force measurementassembly 2000.

In an alternative embodiment, the single load transducer of the forcemeasurement assembly 2000 may be in the form of a force transducer beam,rather than a pylon-type load transducer 2014.

In the illustrative embodiment, the top plate component 2002, the topadapter plate 2006, and the bottom base plate 2030 may be formed fromaluminum or another suitable material.

In the illustrative embodiment, a plurality of force measurementassemblies 2000 are designed to be combined in an array or matrixconfiguration. For example, a first illustrative arrangement 2040 offorce measurement assemblies 2000 is depicted in FIG. 102 . In theillustrative arrangement 2040 of FIG. 102 , two (2) force measurementassemblies 2000 a, 2000 b are arranged in a horizontal configuration(e.g., a 1×2 matrix). As another example, a second illustrativearrangement 2042 of force measurement assemblies 2000 is depicted inFIG. 103 . In the illustrative arrangement 2042 of FIG. 103 , two (2)force measurement assemblies 2000 a, 2000 b are arranged in a verticalconfiguration (e.g., a 2×1 matrix). As yet another example, a thirdillustrative arrangement 2044 of force measurement assemblies 2000 isdepicted in FIG. 104 . In the illustrative arrangement 2044 of FIG. 104, four (4) force measurement assemblies 2000 a, 2000 b, 2000 c, 2000 dare arranged in a square matrix configuration (e.g., a 2×2 matrix). Asstill another example, a fourth illustrative arrangement 2046 of forcemeasurement assemblies 2000 is depicted in FIG. 105 . In theillustrative arrangement 2046 of FIG. 105 , six (6) force measurementassemblies 2000 a, 2000 b, 2000 c, 2000 d, 2000 e, 2000 f are arrangedin a rectangular matrix configuration (e.g., a 2×3 matrix).

Any of the features or attributes of the above described embodiments andvariations can be used in combination with any of the other features andattributes of the above described embodiments and variations as desired.For example, any of the features or functionality described inconjunction with embodiments illustrated in FIGS. 55-74 (e.g.,temperature compensation, crosstalk elimination, or load correctionbased on the position of the applied load) may be utilized in theembodiments of FIGS. 1-54 .

It is apparent from the above detailed description that the presentinvention provides a low profile six-component load transducer 10, 10′,100, 200, 300, 400, 500, 600, 700, 800 which has a significant allowableoffset for the line of action of the force. In that, for a givenallowable maximum load, this load transducer has a much higher momentcapacity than currently available load transducers and the offset valuecan be as high as five times the diameter (or width dimension) of thetransducer. Therefore, the load transducer 10, 10′, 100, 200, 300, 400,500, 600, 700, 800 according to the present invention is able towithstand and measure moments which are approximately ten times higherthan that of a similarly sized and rated conventional load cell.

Also, it is readily apparent that the embodiments of the load transducer900, 1000, 1000′, 1100, 1200, 1300, 1300′, 1400 and the forcemeasurement assemblies 1040, 1150, 1340 using the same offer numerousadvantages and benefits. In particular, the load transducer 900, 1000,1000′, 1100, 1200, 1300, 1300′, 1400 described herein is capable ofbeing interchangeably used with a myriad of different force plate sizesso that load transducers that are specifically tailored for a particularforce plate size are unnecessary. Moreover, the universal loadtransducer 900, 1000, 1000′, 1100, 1200, 1300, 1300′, 1400 describedherein is compact and uses less stock material than conventional loadtransducers, thereby resulting in lower material costs. Also,advantageously, the load transducer 1100, 1200, 1300, 1300′ describedherein is easily machined using a single block of raw material (i.e., asingle block of aluminum) with very little waste because there are onlynarrow gaps between the central body portion and the transducer beamportions. Furthermore, the aforedescribed force measurement assemblies1040, 1150, 1340 utilize the compact and universal load transducer 900,1000, 1000′, 1100, 1200, 1300, 1300′, 1400 thereon so as to result in amore lightweight and portable force measurement assembly.

In addition, it is readily apparent that the embodiments of the loadtransducer system 1550 described above offer numerous advantages andbenefits. In particular, the load transducer system 1550 is capable ofcorrecting the output signal of a load transducer 1510, 1510′ so as toreduce or eliminate the effects of crosstalk among the channels of theload transducer 1510, 1510′. Moreover, the load transducer system 1550is capable of correcting the output signal of a load transducer 1510,1510′ so as to reduce or eliminate the effects of changes in temperatureon the output of the load transducer 1510, 1510′. Furthermore, the loadtransducer system 1550 is capable of accurately determining the appliedload regardless of the location of the applied load being measured bythe load transducer 1510, 1510′.

Further, it is readily apparent that the embodiments of the forcemeasurement system and the calibration method used therewith describedabove offer numerous advantages and benefits. In particular, the forcemeasurement system allows for more versatile transducer designs andminimizes measurement errors. Moreover, the force measurement system iscapable of correcting for load measurement errors resulting from loadsapplied near the periphery of the force measurement assembly.Furthermore, the load calibration process used with the forcemeasurement system results in more accurate load measurements bycorrecting the computed load based upon the applied position of theload. In addition, a force measurement system is described above that iscapable of assessing the fall risk of a subject based upon a combinationof balance parameters.

From the foregoing disclosure and detailed description of certainpreferred embodiments, it is also apparent that various modifications,additions and other alternative embodiments are possible withoutdeparting from the true scope and spirit of the present invention. Theembodiments discussed were chosen and described to provide the bestillustration of the principles of the present invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the presentinvention as determined by the appended claims when interpreted inaccordance with the benefit to which they are fairly, legally, andequitably entitled.

The invention claimed is:
 1. A force measurement assembly configured toreceive a subject, the force measurement assembly including: a topcomponent, the top component having a top surface for receiving at leastone portion of the body of the subject; a single force transducersupporting the top component, the single force transducer including aforce transducer body portion with at least one wall and at least onedeformation sensing element disposed on the at least one wall of theforce transducer body portion, the single force transducer configured tosense one or more measured quantities and output one or more signalsthat are representative of forces and/or moments being applied to thetop surface of the top component by the subject, the at least one wallof the force transducer body portion configured to be deformed as aresult of the forces and/or moments being applied to the top surface ofthe top component by the subject, the at least one deformation sensingelement extending across a wall surface of the at least one wall andbeing configured to undergo deformation with the at least one wall ofthe force transducer body portion, and the single force transducersupporting the entire weight of the top component; and a base componentdisposed underneath the single force transducer, the base componentconfigured to be disposed on a support surface; wherein the forcemeasurement assembly is configured to be combined with one or more otherforce measurement assemblies as part of a force measurement system. 2.The force measurement assembly according to claim 1, wherein the singleforce transducer is disposed proximate to a center of the top component.3. The force measurement assembly according to claim 1, furthercomprising a data processing device operatively coupled to the forcemeasurement assembly, the data processing device configured to receivethe one or more signals that are representative of the forces and/ormoments being applied to the top surface of the top component by thesubject, and to convert the one or more signals into output forcesand/or moments.
 4. The force measurement assembly according to claim 1,wherein the single force transducer is in a form of a pylon-type forcetransducer.
 5. The force measurement assembly according to claim 1,wherein the single force transducer comprises a force transducer beam.6. The force measurement assembly according to claim 1, wherein thesingle force transducer is configured to measure at least one forcecomponent and at least one moment component.
 7. The force measurementassembly according to claim 6, wherein the single force transducer isconfigured to measure a plurality of force components and a plurality ofmoment components.
 8. The force measurement assembly according to claim1, wherein the single force transducer defines a force transducerfootprint, and the top component is in a form of a top plate with thetop surface for receiving the at least one portion of the body of thesubject, the top plate defining a plate footprint that is larger thanthe force transducer footprint of the single force transducer.
 9. Theforce measurement assembly according to claim 1, wherein the singleforce transducer defines a force transducer footprint, and the basecomponent is in a form of a bottom plate configured to be disposed onthe support surface, the bottom plate defining a base footprint that islarger than the force transducer footprint of the single forcetransducer.
 10. A force measurement assembly configured to receive asubject, the force measurement assembly including: a top componentdefining a top component footprint, the top component having a topsurface for receiving at least one portion of the body of the subject; asingle force transducer supporting the top component, the single forcetransducer including a force transducer body portion with at least onewall and at least one deformation sensing element disposed on the atleast one wall of the force transducer body portion, the single forcetransducer defining a force transducer footprint, the single forcetransducer configured to sense one or more measured quantities andoutput one or more signals that are representative of forces and/ormoments being applied to the top surface of the top component by thesubject, the at least one wall of the force transducer body portionconfigured to be deformed as a result of the forces and/or moments beingapplied to the top surface of the top component by the subject, the atleast one deformation sensing element extending across a wall surface ofthe at least one wall and being configured to undergo deformation withthe at least one wall of the force transducer body portion, the singleforce transducer supporting the entire weight of the top component, andthe top component footprint being larger than the force transducerfootprint of the single force transducer; and a base component disposedunderneath the single force transducer, the base component configured tobe disposed on a support surface; wherein the force measurement assemblyis configured to be combined with one or more other force measurementassemblies as part of a force measurement system.
 11. The forcemeasurement assembly according to claim 10, further comprising a dataprocessing device operatively coupled to the force measurement assembly,the data processing device configured to receive the one or more signalsthat are representative of the forces and/or moments being applied tothe top surface of the top component by the subject, and to convert theone or more signals into output forces and/or moments.
 12. The forcemeasurement assembly according to claim 10, wherein the single forcetransducer is disposed proximate to a center of the top component. 13.The force measurement assembly according to claim 10, wherein the singleforce transducer is in a form of a pylon-type force transducer.
 14. Theforce measurement assembly according to claim 10, wherein the singleforce transducer comprises a force transducer beam.
 15. The forcemeasurement assembly according to claim 10, wherein the single forcetransducer is configured to measure at least one force component and atleast one moment component.
 16. The force measurement assembly accordingto claim 15, wherein the single force transducer is configured tomeasure a plurality of force components and a plurality of momentcomponents.
 17. The force measurement assembly according to claim 10,wherein the top component is in a form of a top plate with the topsurface for receiving the at least one portion of the body of thesubject.
 18. The force measurement assembly according to claim 10,wherein the base component is in a form of a bottom plate configured tobe disposed on the support surface, the bottom plate having a basefootprint that is larger than the force transducer footprint of thesingle force transducer.